试题题干
WORD FORMATION
Complete the following sentence with the proper form of the word in the bracket.
(fortunate) The life guard on duty was walking on the beach that bay, but 
he didn't notice the woman who was drowning.
参考答案
试题解析
but表转折，前后应该是语意的转折。
前面是说值班的警卫在海湾边走，后面说他没看到有个女士正在溺水。