--Yes. Her classes are always           and interesting.

—I will have an important test tomorrow. I feel stressed now.
—__________ and believe youself. You will pass it.

古代埃及、巴比伦、印度、中国被称为四大文明古国的最主要原因是（    ）

已知数列{a_n}，对任意的n∈N^*，点P_n（n，a_n）都在直线y=2x+1上，则{a_n}为（　　）