Question

Hola, les quería pedir por favor si me pueden ayudar, muchisimas gracias

Use either the present perfect or the simple past as needed.
Examples: — | (visit) visited my sister last night.
I (visit) have visited my sister many times this week.

6. For several years, medical researchers around the world (do) .......... a great deal of research on AIDS.
7. Families (change).......... a great deal in this century.
S. Yesterday in my psychology class, 1 (learn)......... why some people are afraid of being in a small crowded space.
9. I(know) .......... Diana for several years, but 1 just recently (discover) .........that she has a twin sister.
10. Cindy (borrow)............. several books last month and still (return, not)........ them.

Answer 1

Respuesta:

Explicación:

for several years medical researchers did a great deal of research on AIDS.

families changed a great deal this century.

yesterday in my psychology class I learned why some people are afraid of being in a small crowded space

I knowed Diana for several years, but I just recently discovered that she has a twin sister.

Cindy borrowed several books last month and still returned not them