1. I haven't visited my mom for 2 months.
It is + time + since + S + V(QKĐ)
`->` S + have/has + (not) + V3/ed (HTHT) + since/for+ time.
2. Telephone was invented by Alexander.
Câu bị động thì quá khứ đơn:
S + V2/ed + O `->` O + was/were + V3/ed + (by + S)