Exercise 15. Put the verbs in brackets into the correct forms of Present Perfect or Present Perfect Continious: She (to be) ill since last week.
He (to know) this doctor since childhood. He is a pediatrician.
I (to try) to understand your report on the immune response for half an hour.
She (to look) for her stethoscope since she came to the hospital.
The students (to be) in this academy building since 8 a. m..
My sister (to sleep) for ten hours.
Exercise 16. Put questions to the underlined words: The disease may be divided into three main forms according to the anatomical distribution of the membrane.