题目

The annual marathon in my town usually took place in summer. My job was to   31    behind the runners in an ambulance   32     any of them needed medical attention. The driver and I were in an air-conditioned ambulance behind nearly one hundred athletes    33    to hear the sharp crack of the starting gun. “We’re supposed to stay behind the   34    runner, so take it slowly ,” I said to the driver , Doug , as we began to creep forward . “Let’s just hope all the runners are fast!” he laughed. As they began to pace themselves, the front runners started to    在下面的四个几何体中，它们各自的左视图与主视图不一样的是（ ）A．正方体B．正四棱台C．有正方孔的正方体D．底面是长方形的四棱锥