①In order to protect our environment, we can't freely cut trees without the government's ____(允许)．

②There is no ____ (通路) to the street through that door.

③Humor is a more effective ____(防御) than violence(暴力)．

④Now that you are a college student, you should learn to be ____ (独立的)of your parents' help.

⑤Can you give me a ____(明确的)answer by tomorrow?

⑥With his new method, the time of the project will be ____ (缩短)．

⑦They brought the piano ____(斜着地) through the front door.

如图，直径为10的⊙A经过点C（0，5）和点O（0，0），点B是y轴右侧⊙A上一点，则cos∠OBC的值为（   ）

下图为纳米比亚局部区域图。海豹是肉食性海洋动物，克罗斯角的海豹自然保护区不到1平方千米的海滩上，常年积聚着8万～10万头海豹。图示地区可观赏“到沙入海”的奇观；红色沙漠依偎着蔚蓝的大西洋，高大沙丘的滚滚沙流飞泻入海，这种奇景的形成原因是（   ）