找出所给问句的对应答语。

①Can I help you?                                ____                     A. I'd like some oranges.

②What do you need?                          ____                     B. Three.

③How many books do you want?        ____                     C. Yes, I think so.

④Is that all?                                         ____                     D. Yes, I need some milk.

⑤What would you like?                        ____                     E. I need some fish.

拼音我最棒。

读图，完成下题。

用数学归纳法证明 $\frac{1}{1\cdot 2}+\frac{1}{2\cdot 3}+\frac{1}{3\cdot 4}+\cdots +\frac{1}{n\left(n+1\right)}=\frac{n}{n+1}$ （n∈N^*）时，由n=k到n=k+1，等式左端应增加的式子为（   ）

下列有关化学史的叙述错误的是（   ）