题目3单选题
质点的运动学方程为 <img src="https://tihai-oss-cloud.itihey.com/img/e923037a046f790d59db3af3b2a1bb60.png">,则质点的速度为()A. <img src="https://tihai-oss-cloud.itihey.com/img/421d71c95583a85637e5ec6f13f641fd.png">B. <img src="https://tihai-oss-cloud.itihey.com/img/5b9c349f20b4a012b81296bd9fa51708.png">C. <img src="https://tihai-oss-cloud.itihey.com/img/d8290556a60c77633374077df5fea820.png">D. <img src="https://tihai-oss-cloud.itihey.com/img/a2b558cfe7f1f06be3fda413b3b08535.png">