Has he been working
Yes, he... (to work) since morning. has been working
The Sierra Club... (be) an organization whose goals center on the protection of the environment. is
The Sierra Club is an organization whose goals... (center) on the protection of the environment. center
It... (found) in 1692 in San Francisco by naturalist John Muir, who was intent on preserving the natural beauty and harmony of Sierra Navadas in eastern California. was founded
It was founded in 1692 in San Francisco by naturalist John Muir, who... (be) intent on preserving the natural beauty and harmony of Sierra Navadas in eastern California. was
Today the Sierra Club... (boast) almost 200,000 members in all fifty states of the United States. boasts
Through activites such as conferences, lectures, exhibits, expeditions, and films, the organization... (to work) to continue the effort begun by John Muir. works
The Sierra Club also... (publish) a weekly newsletter, a bimonthly magazine, and various books. publishes
A transistor is an active semiconductor device with three or more electrodes. By active... () that the transistor is capable of current gain, voltage amplification and power gain. is meant
A transistor is an electronic device in which electronic conduction... () within a semiconductor. is made
A semiconductor is an electric conductor with resistively in the range between metals and insulators, in which the electrical charge carrier concentration... () with increasing temperature over some temperature range. rises
The resistivities of semiconductors and insulators... () rapidly with rising temperatures, while those of metals increase relatively slow. Unlike metals and insulators, the resistivity of semiconductors depends upon the direction of current flow. decrease
The resistivities of semiconductors and insulators... () rapidly with rising temperatures, while those of metals increase relatively slow. Unlike metals and insulators, the resistivity of semiconductors depends upon the direction of current flow. decrease
The direction of the easiest current flow or lowest resistively... () the forward direction, the direction of restricted current flow or highest resistively is known as the reverse or back direction. is called
The direction of the easiest current flow or lowest resistively is called the forward direction, the direction of restricted current flow or highest resistively... () as the reverse or back direction. is known
A dividend... only be paid out of profits but not out of capital. can
famous business partnership in English history. were able
The owners of a private company... be members of the same family. can
Typewriting courses... combine keyboard training with the theory and practice of typewriting. can
We... install a fax machine yesterday. were able to
The interviews begin on Tuesday, each interview... last not more than 30 minutes. can
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They... start earlier than 9.30 as it takes time to get to the place of the interviews and fulfill all the necessary formalities. cant
No interviews... scheduled after 4.30. can be
An interview... take place between 1.00 p.m. and 2.00 p.m. as it is lunch-time. cant
The participants... come on Monday as they were warned beforehand. cant have
They... be waiting for begining now as it is only 8.30. cant
Many business people prefer the flexibility, reliability and convenience of a hire car to using their own car. Car hire... be particularly useful and advantageous when combined with air travel. can
The major international car rental firms... provide a special programme designed specially for business people. can
This... include a Rent it here. Leave it theres service. can
Different sizes and types of cars... be available. can
Some firms... provide a driving directions service. can
Computerized systems... provide an instant containing step-by-step directions to the destination. are to
When a hired car is required you... book in advance. have to
The rates are usually cheaper and availability... be guaranteed. is to
When selecting and In some countries a driving license of your country is not acceptable; your... have an international driving permit. need to
For a small charge permits... be issued to any current holder of valid driving license. can
You... always check the driving regulations for the countries concerned. must
Are these sentences right or wrong?
An operator should know how to use the telephone system.
An operator can know how to use the telephone system.
An operator may know how to use the telephone system.
