It is very difficult to retain all that you hear in the class.
Answer: Option A
Solution(By Examveda Team)keep : have or retain possession of.
recall : bring (a fact, event, or situation) back into one's mind; remember.
preserve : maintain (something) in its original or existing state.
conserve : protect (something, especially something of environmental or cultural importance) from harm or destruction.
retain : continue to have (something); keep possession of.
Synonym of retain is keep
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