appeared to have

问题描述:

appeared to have
he was surprised by the strength of the effect that owning a cat appeared to have.

定语从句.先行词the effect,关系代词that,the effect就是后面have的宾语.
在这个从句中,从句主语是owning a cat——动名词作主语,appeared to作从句谓语.appear to do 是词组“似乎,显得……,表面上看……”,你应该把它跟have分开来理解.
“他被/似乎养只猫/就能带来这样的效果/吓了一跳.”