Chọn C
Since my grandfather learnt to use Facebook, he ______ many interesting stories on it.
I ______ an online class in Advanced Maths when the Wi-Fi got disconnected.
Hung used to go swimming during summer months when he ______ young.
Only after Nam ______ out of the exam room did he realise that he had forgotten to bring his calculator.
While he ______ some plants in the garden, his wife was preparing dinner.
Phillips will have lived in this small town for five years ______ .
Our village ______ cleaner since some environmental campaigns were launched.
She had worked for 10 different enterprises before she ______ her own company.