Bonjour
a- They visited their cousins in Canada last summer.
action passée terminée
b- Mary was jogging in the park when it started raining.
action en cours be + ing > passé < action soudaine
c- Did you catch any fish in this river ?
interrogation au passé = auxiliaire DID + sujet + Base Verbale
d- Hurry up ! They are waiting for us !
action présent en train de se passer = be + -ing
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bonne journée ☺☺☺