1948年的最后一天，蒋介石在日记中写道：“本月忧患最深…各方告急与失败之报，几如雪花飞来，…一切唯听天命而已。”蒋介石这种心态主要是因为（    ）

计算： ${(-\frac{1}{2})}^{-2}$ + $\sqrt{3}$ tan60°+|-1|+（2cos60°+1）⁰.

阅读下面一则学校海报，选择正确答案。

SCHOOL EVENTS

OPEN DAY（开放日）：

AUGUST 16th, 2012 9:00 ~ 12:00 a.m.

All parents can come to our school, have a cup of coffee, and meet our teachers and other parents.

Parents can go to the classrooms of 12 ~ 15 years old, have a talk with the principal (校长), have a look at the clubs and ask any questions.

All requirements（要求）for a happy school are welcome.

Lunchtime: 11:30 ~ 12:00 a.m.

Please go to Room 305 for lunch.

All parents are welcome. Please contact (联系) us.

Contact: Melodie Lezar, the principal

TEL: 021- 4615998

E-mail: disapark@ telkoms.a.net

School: Goodwin Middle School