Choose the correct verb form:

____ 60,000 people filled the stadium.

Those of you who signed up Dr. Daniel’s anthropology class should get their books as soon as possible

We must be very careful with sensitive issues such like this, to avoid giving offence

He's finished this test, _    ?

Researchers in economics, psychology, and marketing can help businesses.

We had to turn _______ their invitation to lunch as we had a previous engagement. 

Because the tachinid fly is a parasite of harmful insects, much species have been imported into United States to combat insect pests

Among the parameters that determine whether an environment is suitably for life as we know are temperature, water availability,oxygen content.

Of all outdoor activities, Paul likes fishing best of all, but he doesn’t enjoy cleaning the fishing afterwards

Bronze, after being heated by a strong flame, will change color, especially when exposure to hydrogen

She sighed with relief when she found out that she has passed the test

Short-wave radios can receive and transmit signals are used by pilots, the police, and amateur operator.

You needn’t do that when the maid is here, _____?

What are common known as “lead” pencils are not lead, but  a mixture of graphite, clay and wax.

The intent of the Historical Society is to restore old buildings and the increase of interest in history of area.

Mutualism is relationship between animal species which in both benefit .

California has more land under irrigation than other state

I try to go jogging at least four times _______ week.

The accounting supervisor was unpleased to learn that the budget report would no finished by time.

First raise your right hand then, you should repeat after me.

Do it right now, ______?