42. According to the article, why did the number of experiments involving space animals increase in the 1960s? (A) The United States and Soviet Union needed data about space travel in order to be the first to land a human on the moon (B) The United States was collecting information about space so the Soviet Union could put a dog into orbit (C) The Soviet Union and the United States were working together to put a human being on the moon (D) The United States and the Soviet Union believed that space was simply too dangerous for human beings and only animals could safely travel there