Look at the exemples and complete the explanations
1) 1665,Isaak Newton made an in important discovery
We use the past ... for comleted actions in the past
2)He was studying at Cambtige University
We use the past ... to describe the situation at a particular time in the past
3)He was sittinv under a trer when an apple fell on his head
We use the ...... and ...... together when one action was in progress action interrupted it.
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