2道托福语法题目虚心请教各位!!

lhj2226157UID: 2182194

选错:
1. because of its vast tracts of virtually uninhabited northern forest,canada has    one of the lowest population density in the world.
2. composer richard rodgers and lyricist oscar hammerstein 2 brought to the muscial oklahoma extensive muscial and theatrucal backgrounds as well as familiar with the traditional forms of operetta and muscial comedy.
哪里错了?为啥?

yeshunUID: 2117489

1 one of 后面是复数 density-->densities
2 并列结构 familiar-->familiarity