That Social Security payments will be a burden comes from the concern that________

* Hướng dẫn giải

Đáp án là C

Trong câu: “Recently, there has been concern that the Social Security fund may not have enough money to fulfill its obligations in the 21st century (=Social Security payments will be a

burden) , when the population of elderly Americans is expected to increase dramatically (= the number of elderly people is growing).