四、完形填空练习

　　阅读下面短文，其中有十处空白，根据短文的内容在文中的空白处填上适当的字母，使之构成一个完整的单词。该单词的第一个字母已经给出。

　　Heart

　　The heart is really just a very strong pump. It has four valves made of vry thin, strong tissues. If the damage to the h( 1 is not too bad, we put in pieces of natural heart-valve, which are taken from other people w ( 2 have just died. If a damaged artery is not too big, we replace it with a piece of vein. We take the v( 3 from another part of the patient’s own body. The human body has more veins than it really needs.

　　But how can we operate on the heart? how does the blood continue to flow round the b( 4 ? Here the engineers really have helped us. We use the heart-lung machine. It does the work of both the heart and the l( 5 . It pumps the patient’s blood out of a large vein near the heart and passes the blood through a ’bath’ of oxygen. The b( 6 is filled with oxygen, and other gases are taken away from it, as in our lunges. The m( 7 keeps the blood warm all the time. Then it pumps the blood back into a large artery. It does all this in a very gentle way, the blood c( 8 are not damaged. So we can work on a heart which is empty of blood.

　　"If you aren’t breathing, and if our heart isn’t beating, you are d( 9 ," people used to say. But that is not true now. Although the heart is not pumping, and the patient is not breathing, his blood is still going around his body w( 10) the help of the machine. He is very much alive. The heart-lung machine saves thousands of lives every year. It’s really a wonderful invention!