单项选择题What affects the amount of carbon-14 on earth
单项选择题According to this passage, the best way to build a good vocabulary is ______.
单项选择题The moment the author got down to the river bank he saw
单项选择题Which of the following is true
单项选择题From the text we can infer that () led to the sinking of the submarine Kursk.
A. a small fighting with another foreign submarine B. an explosion inside the submarine Kursk C. a great collision inside the submarine Kursk D. an attack from another foreign submarine