A:if
B:how
C:that
D:what
The headmaster introduced ______ to the German visitors before the welcome party.
(1)计算:(π﹣3)0+(12)﹣1﹣27﹣tan30°;
(2)解方程:3x2-9+xx-3=1;
(3)解不等式组3y≥y+24y-2<y+4,并把解集在数轴上表示出来.
English is very____ (interest). I like it very much.