题目内容：

The green turtle is listed as endangered by the International Union for the Conservation of Nature. Under the U．S. Endangered Species Act of 1973, the green turtle was listed as threatened except for the breeding populations in Florida and on the Pacific coast of Mexico, where it is listed as endangered.

Green turtles continue to be caught for money by humans, and the destruction and loss of nesting and foraging(觅食)sites is a serious problem. Humans have already caused the decrease of large green turtle populations, including those that once nested in Bermuda and Cayman Islands. The situation of green turtle populations is difficult to determine because of our lack of knowledge about their life cycles. The number of nests in Florida appears to be increasing, but we don't know whether this is due to an increase in the number of nests or because we have started to monitor(监控)nesting beaches more closely.

The green turtle is the largest hard­shelled sea turtle. Adults of this species commonly reach 100 cm in length and 150 kg in mass. The average size of a female nesting in Florida is 101.5 cm straight in length, with an average body mass of 136 kg.

Growth rates of green turtles have not been measured under natural conditions. Green turtles grow slowly.

In the southern Bahamas, green turtles grow from 30 to 75 cm in 17 years, and according to Bjorndal and Bolten, growth rates decrease with increasing length. Growth rates measured in green turtles from Florida and Puerto Rico fall within the range of growth rates measured in the southern Bahamas. Based on growth rate studies of wild green turtles, the researchers Balazs, Frazer and Ehrhart estimate the age of sexual maturity(成熟)can range anywhere from 20 to 50 years.

1.The main idea of the passage is to tell us________.

A．something about an endangered animal

B．how green turtles got extinct

C．how heavy a green turtle is

D．how long a green turtle can live

2.Which of the following is NOT a reason why green turtles are endangered?

A．Humans catch them to get profit.

B．They lose their nests.

C．They have fewer places to find food.

D．People like to keep them as pets.

3.According to the passage, the green turtle________.

A．can reach 100 cm in length in 17 years

B．lives in the sea and grows very slowly

C．lives only in Florida and on the Pacific coast of Mexico

D．can grow from 30 to 75 cm in 17 years in southern Florida

4.Why is it hard for us to know the number of green turtles?

A．Because it is difficult for us to be close to them.

B．Because we have limited knowledge about them.

C．Because we haven't measured their growth rates.

D．Because they grow too slowly.