填空题

A strict vegetarian is a person who never in his life eats anything (36) from animals. The main (37) to vegetarianism on a long-term basis is the difficulty of getting enough protein—the (38) element in food. If you have ever been without meat or other animal foods for some days or weeks (say, for (39) reasons), you will have noticed that you tend to get (40) rather weak. You are glad when the fast is over and you get your reward of an (41) meat meal. Proteins are built up from (42) 20 food elements called ’amino-acids’ (氨基酸), which are found more (43) in animal protein than in vegetable protein. This means you have to eat a great deal more vegetable than animal food in order to get enough of these amino-acids. A great deal of the vegetable food goes to waste in this process and (44) . The economic side of the question, though, must be considered. Vegetable food is much cheaper than animal food. (45) , a consistent vegetarian, if he is to gain the necessary 70 grams of protein a day, has to consume a greater bulk of food than his digestive organs can comfortably deal with. (46) .