支配骨骼肌的躯体运动神经纤维释放的递质是（）

A．肾上腺素

B．去甲肾上腺素

C．乙酰胆碱

D．γ-氨基丁酸

One day a businessman was going to another town to sell his goods (货物). He decided to take ten servants(仆人) with him. They would carry his goods and also some food to eat on the way. He said to one of the servants, "You are the smallest and the shortest one. You may carry the lightest load (担子). "The servant thanked him but took the biggest load. This was the bread to eat on the way.
The man said, "You’re foolish. That is the heaviest load." But the servant took up the load happily, and so they set off. After four hours they stopped for a rest. They all ate some of the bread. Then there was less bread for the servant to carry. Every time they ate some bread, the load became smaller and lighter. At the end of the trip, the servant had nothing to carry, and all the other servants still had a lot of things to carry.

They stopped ______ to eat some bread and have a rest.
A. three timesB. twice C. some times