Beginner Level 初级 (chūjí)
The right answer for this online Chinese class is B.
You now know that “Can I help you?” in Chinese is “我能帮你吗? (Wǒ néng bāng nǐ ma?).” In different contexts, people use different Chinese expressions and grammar. If you want to offer help to another person, you should say “我能帮你吗? (Wǒ néng bāng nǐ ma?)”
In situation A, the little boy could say “对不起(Duì bù qǐ.).” This means “I’m sorry.” In situation C, the old lady should say “谁的钱? (Shuí de qián?)” This means “Whose money?”