There was no altruistic motive that prompted him to help her.

Altruistic refers to showing a disinterested and selfless concern for the well-being of others; unselfish. The opposite of the word is selfish, which is there in Option B.

Option A- Brutal means violent, cruel, or harsh, which is not the direct opposite of altruistic. 

Option C- Inhuman means lacking compassion or empathy, which is somewhat the opposite but not the best choice.

Option D- Wicked means evil or morally wrong, which is not the exact opposite of altruistic.