According to the T-Boat regulations the reason for providing adequate ventilation for a battery storage area is to prevent（）.

A.accumulation of carbon dioxide gas that chokes the battery

B.accumulation of explosive and toxic gases the battery can generate

C.mildew or dry rot in the battery box

D.battery failure including battery case meltdown caused by excessive heat

数据独立性分为逻辑独立性与物理独立性。当数据的存储结构改变时,其逻辑结构可以不变,因此,基于逻辑结构的应用程序不必修改,称为【 】。