If you think you have a puncture（漏气), first check the valve（气阀) to make sure air is no

If you think you have a puncture(漏气), first check the valve(气阀) to make sure air is not leaking from it, by putting spit on the end of it. If the valve is not the source of the leak, remove the wheel from the bicycle and put the tyre off. Be careful not to pinch the inner tube. Remove the inner tube and pump some air into it. Then hold it in a bowl of water until you see bubbles coming from it. Or, hold the tube to your ear and listen for air escaping. Dry the tube. Choose a patch which is big enough to cover the hole and the surrounding area. Apply glue to tube before sticking patch down. Before you put the tube back in the tyre, run your fingers over both the inside and outside of the tyre to make sure that whatever caused the puncture is not still there. To replace the tube, put the valve part way through the hole in the rim(轮圈), pump a little air in, and then feed it carefully under the tyre. Push the tyre over the rim and back into position. Do not use tyre levers for doing this. Pump up the tyre fully and replace the wheel on the bicycle. Make sure the wheel is positioned in the center of the frame.

This passage is intended for someone who ______.

A．learn to ride a bicycle

B．has a flat tyre

C．buys a new tyre

D．travels by bike