2. Choose the correct variant.

The problem of ____ the machine respond to the presence of objects in different places has already been solved.

a) make
b) making
c) to make
d) be making
e) to making

3. Choose the correct variant.

In games, for example, the ____
boards, cards, dice, and other equipment are merely objects.

a) being played
b) to play
c) play
d) playing
e) to be playing