$42.$ A
- Before + S + V (-ed/ bất quy tắc), S + had + V (Pii).
$43.$ D
- S + haven't/hasn't + V3 +time = It is + time + since + S + last + V2.
$44.$ C
- S + began + V-ing + time + ago = S + have/ has + V3 + for + time.
$45.$ A
- The last time + S + V2 + was + time + ago = S + haven't/hasn't + V3 + for + time.
$46.$ A
- S + haven't/hasn't + V3 +time = It is + time + since + S + last + V2.
$47.$ C
- S + V2 + time + ago = S + have/ has + V3 + for + time.
$48.$ A
- S + haven't/hasn't + V3 +time = It is + time + since + S + last + V2.
$49.$ B
- It is + time + since + S + last + V2 = S + haven't/hasn't + V3 +time.
$50.$ D
- The last time + S + V2 + was + time + ago = S + haven't/hasn't + V3 + for + time.