Faced with this new situation, people have 30 to find out how to deal with it.
答案：(B) yet
have yet to V 意為「尚未做某事」，本身即帶否定語氣，指人們面對這個新情況還沒找出因應之道；not 無法構成 have not to 這種說法，till 與 though 也接不上不定詞。
答對率 32%。
yet 你大概只會用在句尾（I haven't finished yet.）。這裡它夾在 have 與 to 中間，句子又看不到 not，所以讀不出否定的意思。
它自己就是否定，不能再加 not。最快的理解方式是換句話說：have yet to V ＝ still haven't + p.p.。He has yet to find an investor. ＝ He still hasn't found an investor.（他至今還沒找到投資人）。本句 people have yet to find out how to deal with it ＝ 人們還沒找出因應之道，正好呼應前一句的 we do not know what will become of it。
很多人是把 till 看成 still。till ＝ until（直到），後面接時間點或子句（Wait till Monday.）；still ＝ 仍然，放一般動詞前、be 動詞後（She still lives here.）。就算你把 till 讀成 still，選項印的仍是 till，而 till 接不上不定詞 to find out，句子直接不成立。
have not to 不是英文；though 是連接詞，接不上不定詞。
have yet to V（尚未做某事）、be yet to be decided（尚未決定）、as yet（迄今為止）、not yet（還沒）。
It is a usual sunny afternoon in the village of Midwich, England. It seems not 21 any afternoon in the village, but all of a sudden, people and animals lose consciousness. 22 they awake, all of the women of child-bearing age have become pregnant.
This is an episode from a 1960 science fiction story. The women in the story 23 birth to children that have the same appearance. They all have blond hair and "strange eyes." 24 the children grow, they run around the village in a pack, wearing identical clothing and hairstyles, staring at everyone impolitely. 25 one child learns is also known by the others instantly. Villagers begin to 26 their belief that the children all have "one mind."
In this story, the children are produced by some unexplained force from outer space. But this story written 40 years ago 27 predicted the arrival of a recent method of genetic engineering—cloning. Cloning is the genetic process of producing copies of an individual. Will the genetic copies of a human really have "one mind" as 28 in this story? This situation is so strange to us that we do not know what will 29 of it. Faced with this new situation, people have 30 to find out how to deal with it.