从下图可以读取的信息有( )
①蒸汽机已运用于交通运输 ②工业革命在一定程度上牺牲了环境 ③世界市场最终形成 ④有利于冲破封建等级观念
A:①②
B:①②④
C:②③
D:①②③④
Tom is ________ his pen, but he can't ________ it. Let's help him.
(Ⅰ)求数列{an}的通项公式;
(Ⅱ)设bn=(﹣1)nlog2an,求数列{bn}的前2017项和T2017.