用方框中所给短语的适当形式填空
keep fit,say no to,be worried about,thanks to,health care
Carol doesn't know what she should take for her trip. (改为同义句)
Carol doesn't know____ ____ ____for her trip.
一共有____个图形。 有____个, 有____个, 有____个, 有____个。
S1=1
S2=2+3=5
S3=4+5+6=15
S4=7+8+9+10=34
S5=11+12+13+14+15=65
S6=16+17+18+19+20+21=111
S7=22+23+24+25+26+27+28=175
…
可得S1+S3+S5+…+S2n﹣1=____.