be動詞平衡

jeffyang

一般來說是不是只要be動詞前面是 Ving 或是 To V
後面就要是對應的 Ving 或是 To V，
而不能是 Ving ... is N. 這種用法
我在文法書裡面看到的是這樣
但是我也看到這種用法.
The only way you shoud do is to get up early.
這樣不就是不平衡了 ?

再舉一個例子 OG#84
One legacy of Madison Avenue’s recent campaign to appeal to people fifty years old and over is the realization that as a person ages, their concerns change as well.
(A) the realization that as a person ages, their
(B) the realization that as people age, their
(C) to realize that when a person ages, his or her
(D) to realize that when people age, their
(E) realizing that as people age, their

(C)(D)(E)
不選的原因，也是因為One legacy 與 to realize 或是 realizing不平衡..

有點搞混了，希望大家指導指導....