Choose the answer which correctly completes the sentence

1. 
   Choose the answer which correctly completes the sentence.
   

Rabies … an ordinarily infectious disease of the central nervous system, caused by a virus and, as a rule, spread chiefly by domestic dogs and wild flesh-eating animals.

1. 
   Are B) is C) were D) to be
   

2. 
   Choose the answer which correctly completes the sentence.
   

No one knows exactly how people learn a language … a great deal of research has been carried out on the subject.

1. 
   Despite B) Because C) Although D) So that
   

3. 
   Choose the answer which correctly completes the sentence.
   

Many modern investigators have done research in the field of sleep and … conclusions have often, differed widely. Yet … all have agreed on one point: sleep is nature`s great restorer.

1. 
   Our/ourselves B) his/ours C) your/him D) their/they
   

4.