1 In most cases, the acoustics of a room ------- if a proper balance between sound-absorbing and sound-reflecting materials is created.

A satisfactorily

B will satisfactorily

C will be satisfactory

D to be satisfactory

2 The twin-lens reflex camera has two lenses, ------ for focusing and view finding and the other for recording the photographic image.

A of which one

B one that

C and one

D one

3 In the twentieth century, ------- clear that vaccines immunize the body by artificially stimulating the formation of antibodies.

A it became

B became

C to become

D there became

4 The face is the most ------- of a human being.

A part is distinctly

B distinction in part

C distinctive part

D part of distinction