Past perfect

We ______ different things before we found a solution.

• have tried

• have tryed

• had tryed

• had tried

After she ________ a new machine, she won a prize.

• has invented

• had invented

• invented

• invents

The class ___________ when we got to the science laboratory.

• had just started

• just had started

• had started just

• has just started

When I _____ him, Mark ________ his experiment.

• see

• saw

• had finished

• had finish

_________ any inventions before they invented this product?

• They had created

• Had created they

• Had they created

• Had they create

Before I ________ this one, I __________ a lot of other products.

• chose

• choose

• had tested already

• had already tested

Past participle verb see

Past participle verb to find

Past participle verb to cook

She ________ for months before she found a solution.

• has worked

• have worked

• had worked

• works