The major problem of water efficiency in industry is a______.

A．He fed the dog happily.
B．He picked up the dog by the tips of its ears.
C．He sat in a chair with the dog dangling beside him.
D．He made people laugh by kissing the dog’s ears.

A．Dr. Collin.
B．Spray cans.
C．A new type of fuel.
D．A test.