实践的最基本的形式是
A．改造世界的物质活动
B．改造自然的生产劳动
C．一切创造性活动
D．推动历史进步的活动
答案：B
The first use of atomic weapons was in 1945. and their power _____ increased enormously ever since.
A．is
B．was
C．has been
D．had been
