我认为AB都对.
I used to think it is easy to learn English well.
其中it做形式主语,真正的主语是to learn English well.
I used to think it easy to learn English well.
其中it做形式宾语,easy做宾补,真正的宾语是to learn English well.
同样,第二句话I find it is easy to grasp it now.
it做形式主语,真正的主语是to grasp it.
I find it easy to grasp it now.
it做形式宾语,真正的宾语是to grasp it.