（）是长方形强而厚的肌肉，起于下颌骨的下颌角和下颌枝处，主管开口和闭口。
A.咀嚼肌
B.咬肌
C.颞肌
D.表情肌
参考答案：B
先计算前四道找出规律，再按照规律写出最后一道算式的结果．
1+2+1=______=______2
1+2+3+2+1=______=______2
1+2+3+4+3+2+1=______=______2
1+2+3+4+5+4+3-2+1=______=______2
1+2+3+4+5+6+5+4+3+2+1=______=______2
…
1+2+3+…+1999+2000+1999+…+3+2+1=______=______2．
If you feel stressed, you should _______. [ ]
A. keep quiet
B. share your problems with friends or family members
C. shout at your friends and family members
D. be worried about it
