Although cultures may vary, teaching assistants are expected to conform in this respect to American standards. A general rule is that all students expect and deserve equal and professional treatment from their professors and instructors. If you have any doubts about what behavior is considered appropriate, consult your supervising instructor. Ignoring a student or giving an irrelevant answer can cause frustration and even anger. Simply dismissing difficulties of this kind will not solve the problem.
Most people are happy to provide help if it is requested.
The information should be repeated or, better yet, rephrased. Use examples, try the blackboard, charts, or other visual aids if appropriate. If the difficulty is in understanding spoken material, experiment with writing the material down. Quite often students will not admit that they do not understand. The problem may lie with the content or with the English-speaking ability of the teaching assistant.