Раскрой скобки и поставь глагол в present perfect: i (to forget) her telephone number. pupils (to write) their tests. my sister (to go) to the theatre many times. our classmates (to join) the sport club. you (to open) the window, and it is very cold in the classroom.

I have forgotten her telephone number
Pupils have written their tests
My sister has gone to the theater many times
Our classmates have joined the sport club
You have opened the window, and it is very cold in the classroom