The letter ______ a week ago.

• was posted

• is posted

• posted

• was post

Biofuels _________ from different types of plants.

• produced

• are produced

• are produce

• is produced

All the tickets for the concert _________.

• has been sold

• have sold

• have been sold

Now it's too late. Nothing can ________.

• do

• be done

• did

• does

We are sorry about the problem, sir. But don't worry, the mistake ______ right now.

• has been corrected

• was corrected

• is being corrected

English ______ understood in most countries in the world.

• is

• is being

• has been

Our company ________ in 1998.

• was found

• was founded

• founded

• be founded

He ______ promoted and now he is the CEO.

• be

• is being

• has been

Currently, a new product _______ that will solve many future problems.

• is developed

• is being developed

• developes

• be developed

It is important to ______ on the market.

• know

• be known

• is known