英国大炮轰开了中国闭关自守的大门，使一些爱国知识分子从“天朝上国”的美梦中惊醒，一股新思想萌发了。这一新思想的核心是[ ]

A．改革内政，振兴清朝

B．向西方学习，寻求强国御侮之道

C．学习新技术，发展资本主义

D．启迪人民摆脱封建思想束缚

What can be inferred about the defence mechanisms of the sea cucumber

A．They are very sensitive to surrounding stimuli.

B．They are almost useless.

C．They require group cooperation.

D．They are similar to those of most sea creatures.