阅读下面的短文，在标有序号的空白处填入一个适当的词，或填入括号中单词的正确形式，并将相应【答案】写在答题纸上。

So why has English changed   _（80）   _ time? （81）     all languages change and develop when cultures meet and____(82)______ with each other. At first the English spoken in England between about AD 450 and 1150 was very___（83）___   from the English spoken today. It was ___（84）_   more on German than the English we speak at present. Then gradually between about AD 800 and 1150, English became___（85）____ like German because those who ruled England spoke first Danish and later French. These new settlers   （86）      (rich) the English language and especially its ___（87）_   . In 1620 some British settlers moved to America. ___（88）  (late) in the 18th century some British people were taken to Australia too. English began to be _____(89)____ in both countries .

流行病学的研究对象是（）

A.健康人

B.亚临床病人

C.病人

D.疾病

E.人群