问题
单项选择题
3， 15，7， 12， 11，9， 15， ( )。
A．6
B．8
C．18
D．19
答案
参考答案：A
解析：此题是一个隔项数列，其奇数项和偶数项各构成一个等差数列，空缺项是偶数项，偶数项构成的等差数列是15，12，9，由此可以推知下一项应是6，故正确答案为A。
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3， 15，7， 12， 11，9， 15， ( )。
A．6
B．8
C．18
D．19
参考答案：A
解析：此题是一个隔项数列，其奇数项和偶数项各构成一个等差数列，空缺项是偶数项，偶数项构成的等差数列是15，12，9，由此可以推知下一项应是6，故正确答案为A。
I used to hate being called upon in class mainly because I didn’t like attention drawn to myself. And 1 otherwise assignen（指定）a seat by the teacher, I always 2 to sit at the back of the classroom. All this 3 after I joined a sports team. It began when a teacher suggested I try out for the basketball team. At first I thought it was a crazy 4 because I didn’t have a good sense of balance, nor did I have the 5 to keep pace with the others on the team and they would tease me. But for the teacher who kept insisting on my “ 6 for it”, I wouldn’t have decided to give a try. Getting up t he courage to go to the tryouts was only the 7 of it! When I first started 8 the practice sessions, I didn’t even know the rules of the game, much 9 what I was doing. Sometimes I’d get 10 and take a shot at the wrong direction—which made me feel really stupid. 11 , I wasn’t the only one “new” at the game, so I decided to 12 on learning the game, do my best at each prctice session, and not be too hard on myself for the things I didn’t 13 “just yet”. I practiced and practiced. Soon I knew the 14 and the “moves”. Being part of a team was fun and moticating. Very soon the competitive 15 in me was winning over my lack of confidence. With time, I learned how to play and made friends in the 16 — friends who respect my efforts to work hard and be a team player. I never had so much fun! With my 17 self-confidence comes more praise from teachers and classmates. I have gone from “18” in the back of the classroom and not wanting to call attention to myself, 19 raising my hand — even when I sometimes wasn’t and not 100 percent 20 I had the right answer. Now I have more self-confidence in myself. 小题1:
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