50. The frog in the story agreed to carry the scorpion because .
(A) he did not think the scorpion would sting him
(B) he liked to help whoever’s in need
(C) he crossed the river every day
(D) he knew how to swim

A scorpion蠍 and a frog met at the side of a river. 

The scorpion wanted to cross the river, but he didn’t know how to swim. 

“Please, Mr. Frog,” he said, “would you carry me across the river?” “I can’t do that,” said the frog. 

“You are a scorpion, and you will sting蜇 me.” “No,” said the scorpion. “I won’t sting you because then we will both drown in the river.” 

This made sense to the frog, and he agreed to help him. 

The scorpion climbed onto the back of the frog, and the frog began to swim. 

When they reached the middle of the river, the scorpion stung（sting的过去式） the frog. 

It hurt the frog very much, and they both began to sink under the water. 

“Why did you sting me?” asked the frog. “Now I will die, and you will surely drown.” “I couldn’t help it,” said the scorpion. 

“I am a scorpion, and that is what scorpions do. And you knew I was a scorpion when you let me ride on your back.”