Many birds and insects can build ____________ nests to provide shelter for their young.

A．credit cards are usually used irrationally and illegally
B．Americans enjoy buying what they cannot afford
C．products often don't perform as advertised
D．products are more expensive in the U.S. than anywhere else

A．where to buy cheaper things
B．what materials are needed to improve finished products
C．why they purchase some expensive products
D．the brand names of products they buy regularly