Question 24 is based on the passage you have just heard.

听力原文

    An average person consumes 144 pints of milk a year, but 40% of that is poured onto cereal, and 60% of those people are children. But what was once advertised as nutritious is becoming unpopular. (22) [Americans drink 37% less milk than they did in the 1970s.] And in the UK, dairy consumption overall has fallen by a third in the past 20 years. (23) [Milk is increasingly being described in a negative light. A recent blog suggested: “Maybe people are drinking less milk because it is poisonous to many of us.”] Lactose is the sugar found in milk and dairy products. (24) [It needs a series of complex proteins to break it down. Without enough of these proteins, the lactose is broken down by bacteria in the human body. This can cause physical pain and produce gas in the stomach.] However, after we have finished breast or formula feeding, most of us don’t continue producing the complex proteins in our body, which are necessary to break down the lactose. Despite the problems in digesting milk, it does provide many benefits. (25) [Milk is nutritious. It contains vitamins A and D, as well as protein and isn’t full of calories.] You can test yourself by drinking a large glass of milk. If you get sick in your stomach within the next 24 hours, you are lacking the proteins to digest milk.

24. Why does drinking milk cause pain in some people? （为什么喝牛奶会使一些人身体疼痛？）

解析：C。录音中提到，如果人体内分解乳糖的蛋白质含量不足，乳糖就会被人体中的细菌分解。这会引起身体疼痛，并导致胃胀气。由此可知，一些人喝牛奶后身体疼痛是由于缺乏相关蛋白质，C项符合题意，其中的lack...proteins对应录音中的Without enough of these proteins，to digest it对应to break it down，故C项为正确答案。

错项排除：录音中没有提到牛奶饮用量对人体的影响或牛奶中的矿物质，同样也没有提到与牛奶相克的食物，故排除A、B、D三项。