______is called "black carbon" pollution.

Why are mischief makers called "Black Hats"？

A．Because they wear black hats.

B．Because they act in a dishonest way.

C．Because they are magicians.

D．Because they appear in the night.

A．freedom riders.

B．liberation group.

C．Democrats.

D．abolitionists.

The dense black cumulonimbus clouds surrounding the eye of a hurricane are called ______．

A.Spiral rainbands

B.Cloud walls

C.Funnel clouds

D.Cyclonic spirals

A．art and culture.

B．immigrant population.

C．political enthusiasm.

D．distinctive architecture.

Why are many churches called tinder-box？

A．Because they are like boxes

B．For they are made from wood

C．Because they are black churches

D．For they are located on country roads

A、white box testing

B、regression testing

C、black box testing

D、coverage testing