Would you mind _______ quiet for a moment? I'm trying _______ a form.
A：keeping; filling out
B：to keep; to fill out
C：keeping; to fill out
D：to keep; filling out
Read and choose 找出不同类的一项。
先观察算式的特点再填空．
4+8+16=16×2﹣4=28
4+8+16+32=32×2﹣4=60
4+8+16+32+64=64×2﹣4=124
4+8+16+32+…+256=____
a+2a+4a+8a+16a+…+1024a=____
