境内机构在同一银行开立相同性质、不同币种的经常项目外汇账户无需另行由外汇局核准。 ( )

­—Do you know ______ Tom was punished by his father?

—That was ______ he refused to go to school.

A．why; because

B．when; why

C．how; when

D．why; why