题目内容：

语法填空

阅读下面材料,在空白处填入适当的内容（不多于3个单词）或括号内单词的正确形式。

Three months ago George was at the Red Sea and when he came back, brown and happy, he said that he had never had __1.__ a terrific holiday before. As he was very good at swimming and diving and was ___2.__(concern) with biology, he managed to join a scientific research group __3.___ was studying the sea life of the Red Sea coast at that time. The researchers allowed him ___4.__(help) them in their work and gave him a special diving suit, so he was able to stay deep in the sea for quite a long time. George was amazed at ___5.___ beautiful the underwater world was. Millions of brightly colored fish moved __6.____( busy) around him. Crabs, turtles, and sea snakes looked at him curiously and then hurried to do their underwater business. Once, when George followed a little crab, a huge fish appeared from behind a coral rock. Luckily, the shark took no interest __7.___ him and disappeared into the __8.__(deep) as if it had much more important things to do.

While George was working for the group, exploring the sea plants and animals in their natural conditions, he __9.____(make) a firm decision to go on studying biology and natural sciences as research work became very ___10.__(attract) to him.