d. from the 1800s to 1960s 为正确选项。 解题思路:then in the early 1800s the world started to change...people didn’t h**e to explore much any more;by the 1960s most people could expect to live to be at least 60...
h**e to表观需要做的事情,意思是“必须”、“不”。后跟动词原形,称、和数的变化,与情态动词 must 近义。一、 h**e to 的陈述句形式a、 肯定式:h**e to + 动词原形1、 i h**e to tidy my room.我得整理房间。2、 she has to help with the washing.她得帮忙洗衣服。b、 否定式:don't (doesn'...