Present perfect simple and past simple

With the problem of fossil fuel burning, scientists __________ studied lightning because they want to use the energy in lightning.

• hasn't

• has

• have

• haven't

Our parents _____ have computers when they were teenagers.

• did

• has

• haven't

• didn't

Claire, _____ _____ _____ _____ (you ever use) this machine before?

Sure, I _____ _____ (use) one before.

I mean, _____ _____ _____ _____ (you ever make) coffees with this coffee machine?

I see. No, I _____, but I can try.

¹_____ you ever ²_____ any videos on Youtube in other languages?

• 1. Did - 2. watch

• 1. Has - 2. watched

• 1. Did - 2. watched

• 1. Have - 2. watched

Nelson Dellis _____ the Memory Championships in 2011 and 2011.

• won

• 've won

• have won

• has won

When ¹_____ you ²_____ these headphones?

• 1. did - 2. bought

• 1. has - 2. bought

• 1. have - 2. bought

• 1. did - 2. buy

A: ¹_____ you ever ²_____ Japanese?

B: Yes, I ³_____ it when I was a students at university.

• 1. Did - 2. study - 3. 've studied

• 1. Have - 2. studied - 3. studied

• 1. Have - 2. studied - 3. 've studied

• 1. Has - 2. studied - 3. studied