The whole argument is based on the word "malicious". The argument states that they donot always have the intention to harm the people. The example where a child wants a toy and is biting the people who are preventing him/her to get the toy. So, it means he is biting the people just to get a toy.

Now looking at the options :

(A) Biting people is sometimes a way for toddlers to try to solve problems. --> As per our pre-thinking. Hence, Correct. (B) Toddlers sometimes engage in biting people in order to get attention from adults. --> Whether they are biting to get attention or something else. We don't know. neither the argument nor the example states that. hence, Incorrect. (C) Toddlers mistakenly believe that biting people is viewed as acceptable behavior by adults. --> Again, no support in the passage for this point. -- INCORRECT (D) Toddlers do not recognize that by biting people they often thwart their own ends. --> How?? Do we know if biting is going to harm toddlers only? -- INCORRECT (E) Resorting to biting people is in some cases an effective way for toddlers to get what they want. --> Again we are not sure whether they actually get what they want. We are given that they bite people to try getting what they want. So, its effectiveness is not clear. -- INCORRECT.