Optimism is the art of always seeing the glass half full (1) half empty, finding something positive in even the most (2) of situations and last but not least the ability to expect the best even if the chances are (3) . It enables you to try new things, deal with failure as a learning experience (4) a stopping point. In general optimism gives you a reason to live. The world would be a better place if it was full of optimism, (5) unfortunately the trend in today’s youth is (6) the opposite way. Today it is (7) to be pessimistic. One could spend hours discussing how we arrived at this point, (8) our youth refuses to smell the roses and instead prefers to (9) themselves on their own pessimistic (10) .
Optimism is not an (11) gift but rather a learned behavior (12) . Like most behaviors optimism is best learned by watching examples, (13) you. The first step in creating a generation of people with a positive outlook on life, is to (14) life on the bright side yourself. (15) it would be wrong to (16) your child from all negativity, it is important that you are not the (17) of doubts and worries. Finding something positive in a negative situation needs to be (18) Show how to make the best of things by always (19) the positive, by encouraging your child after a(n) (20) and by explaining over and over that failure is just a part of progress.
15（）
A.As
B.Since
C.While
D.Unless
参考答案：C
解析：
该空白处需填入一个从属连词，选择时应考虑主从句的逻辑意义关系。上一句讲自己要成为孩子学会乐观的范例，在生活中要看到光明的一面。本句说“______让孩子避开所有的负面东西是错误的，但自 己也不应该成为怀疑和担忧的来源”，显然，该句前后转折让步关系。[A]As、[B]Since都只能引导时间和原因状语从句；[D]Unless“除非”，引导条件从句；只有While“虽然”能引导让步从句。又如：While he loves his students，he is very strict with them.“虽然他爱他的学生，可是他对学生们很严格。”