The quality of preservation is almost unmatched, and quarry operations have been carried out carefully with an awareness of the value of the fossils. But these factors do not account for the interesting question of how there came to be such a concentration of pregnant ichthyosaurs in a particular place very close to their time of giving birth.
The phrase "account for " is closest in meaning to which of following?
(A) record
(B) describe
(C) equal
(D) explain
正确答案： D