首先我为你提供考题的正确形式：
E28.5 For more than a century, geologists have felt comfortable with the idea that geological processes, although very _, are also_ and so are capable of shaping the Earth, (GIVEN ENOUGH TIME) .
Blank (1)
A slow
B unpredictable
C ponderous
Blank (2)
D intermittent
E steady
F sporadic
注：上面 GIVEN ENOUGH TIME 是我为了把句意更清楚化加的.
选AE.AC都是慢,为什么不选C,而选A?
时常,英语单词的意思要按 “权威”（即英语词典的）定义,
Ponderous 的英语定义是 slow and clumsy（笨拙）because of great weight
比如 clumsy 可以用于有生命的人或动物（比如大象）,但用于地球是不适当的.
E28.9 Once a duckling has identified a parent, the instinctive bond becomes a powerful _ for additional learning since, by _ a parent, the duckling can acquire further information that is not genetically transmitted.
Blank(1)
A inspiration
B channel
C impulse
Blank(2)
D acknowledging
E mimicking
F emulating
选BE.为什么选E而不选F?
既然你已经把选择的范围缩小到E 和 F,咱们就看E 和F 的区别吧.
Mimick – imitate someone’s actions or words 模仿另一个人的举动或语言
Emulate – to equal or excel through imitation,即你说的“模仿,并带有超越的意思”.
区分两者的关键在于定义的 excel （超越）.另外,一个提示是考题说的 instinctive bond （来自本能的孩子和母亲的纽带）,小鸭的本能是模仿妈妈,但要超越妈妈需要一种“意志”和“理智”,小鸭不可能有这种固有的素质.
满意请及时采纳.谢