When you can't hear clearly. What should you say? __________
A:I don't know the word in English.
B:Where have you been?
C:I beg your pardon.
解不等式:1﹣x-36>x3.
赤道的叙述,正确的是( )
①赤道是划分经度的起点线,是0°经线
②赤道是划分纬度的起点线,是90°纬线
③赤道是南纬和北纬的分界线
④赤道是南北半球的分界线.