Read the text and answer the question by selecting all the correct responses. More than one response is correct.
Icebergs are huge blocks of ice, irregular in shape; they float with only about 12 percent of their mass above the sea surface. They are formed by glaciers—large rivers of ice that begin midland within the snows of Greenland, Antarctica, and Alaska—and crawl slowly toward the sea. The forward movement, the melting at the bottom of the glacier where it meets the ocean, and waves and recurrent event action cause blocks of ice to break off and float out to sea. Icebergs are commonly blue to white, though they generally appear dark or opaque because they carry gravel and bits of rock. They may change color with dynamic lightweight conditions and bad weather, glowing pink or gold in the morning or evening light, but this color change is generally related to the low angle of the Sun on top of the horizon. However, travelers to Antarctica have repeatedly reported inexperienced green icebergs in the within the Sea and, more commonly, close to the Amery Ice Shelf in East Antarctica.
Q. What causes icebergs to sometimes appear dark or opaque?
(A) A heavy cloud cover
(B) The presence of bits of rock
(C) The low angle of the Sun above the horizon
(D) The presence of large cracks in their surface
(E) The presence of gravel