题目

BIf you are interested in studying at an American university, you have to take the Test of English as a Foreign Language. The test is widely known as the TOEFL. It is the most widely used language exam for American universities.There are two major kinds of the TOEFL test. The first is the IBT，or Internet based Test. It is offered in most of the world and accepted by nearly every university and scholarship program in the United States. The other kind of the test is called the Paper?based Test or PBT. The PBT is less costly to take and does not require use of the Internet.But how to get starte关于物体运动状态的改变，下列说法中正确的是A.只要物体的速度大小不变，其运动状态就不变B.只要物体的速度方向不变，其运动状态就不变C.只要速度的大小和方向中有一者改变，物体的运动状态就改变了D.只有速度的大小和方向都改变，物体的运动状态才改变了