回答: to reply, to answer...
雪: snow, (literary) to wipe away (a humiliation etc)...
确切: definite, exact, precise...
求助: to request help, to appeal (for help)...
缺失: deficiency, shortcoming, hiatus...
老人: old man or woman, the elderly, one's aged parents or grandparents...
过滤: to filter, filter...
选: to choose, to pick, to select, to elect...
估算: assessment, evaluation...
机遇: opportunity, favorable circumstance, stroke of luck...
