阅读下列短文, 从每题所给的四个选项（A、B、C和D）中选出最佳选项。

      There were three big fish in the lake. One of them, Demo, was wise; another one, Jimmy, was half-wise; Martin, the third one, was stupid.

Some fishermen came to the bank of the lake with their nets. The three fish saw them.

      Demo decided at once to leave, to make the long and difficult trip to the ocean. He thought, "I won't discuss with these two about this. They love this place so much that they call it home and will stay on. How silly they are! They still haven't realized we are in great danger now. Their ignorance will cost them their lives."

      Seeing the wise fish had left, Jimmy thought, "My guide has gone and now I've lost my chance to escape." He felt sorry for it and then thought, "What can I do to save myself from these men and their nets? Perhaps I should pretend（假装）to be already dead, giving myself totally to the water." So he did that. He went up and down with the water, helpless, within arm's reach of the fishermen.

      "Look at this! The best and biggest fish is dead." One of the men lifted him by the tail, and threw him up on the ground. He rolled（滚动）over and over and moved secretly toward the water, and then, back in.

      The third fish was aimlessly jumping about, trying to escape with his speed and cleverness. The net, of course, finally closed around him, and as he lay in the hot frying-pan bed, he thought, "If I get out of this, I'll never live again in the limits of the lake. Next time, the ocean! I'll make it my home."

食品添加剂溴酸钾(KBrO)会致癌，已被禁用，其中溴元素(Br)的化合价为 （   ）