Should be the verb in the past after a conjunction?

[Aaron]

English Language Tests, Intermediate level

ESL/EFL Test #259 "Irregular Verbs Test (7)", question 3

I forgot her birthday but she readily ......... me because I told her about my busy schedule.

(a) forgive
(b) forgave
(c) forgiven

English Language Tests, Intermediate level

ESL/EFL Test #259 "Irregular Verbs Test (7)", answer 3

I forgot her birthday but she readily forgave me because I told her about my busy schedule.

Correct answer: (b) forgave
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When a sentence start in the past, after a conjunction the verb should be in the past?

Aaron

[Mister Micawber]

.
Not necessarily.

'I woke up at 7:00 this morning, but I won't be ready to go out until this afternoon.'
.
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Native English teacher at Mister Micawber's