mixed tenses

Hardly had the minister finished his speech when the earthquake ___ (shake) the stadium

• had been shaking

• was shaking

• had shaken

• shook

Everybody will be at the office at about 08:30 tomorrow as the meeting ___ (start) at nine o'clock.

• has started

• starts

• will start

• is starting

That candidate who we had been interviewed before we ___ (speak) to all the others is still my favorite.

• were speaking

• was speaking

• spoke

• had spoken

While climbing onto the mountain top, I ___ (encounter) a strange animal which I'd never seen before

• have encountered

• encountered

• was encountering

• had encountered

The president was sure that his plan would work out fine as no other member ___ (oppose) it up to that time

• was opposed

• had opposed

• opposed

• was opposing

I wasn't surprised to hear that Monica (a)   (have) an accident as she is a very careless driver.

Urbanization ___ (always / be) a problem which causes several environmental challenges ever since the rate of migration ___ (increase) after the industrial revolution

(a)  

By the time he was 14, Wolfgang Mozart (a)   (compose) a lot of musical pieces.

By the year 2030, Professor Snape (a)   (teach) Potion for more than 30 years.

By the time the team (a)   (arrive), the competition will have ended