So he keeps on studying after his English classes in order to prepare for life in America.
所以他在英语课下课后还继续学习,为以后在美国生活做准备。
Sometimes the secrecy goes to such an extent that the whole nature of the research cannot be mentioned.
有时,保密竟达到了这样的程度,即连研究工作的整个性质都不准提及。