Psychological studies show that some people are quick-tempered .A. at heartB. on purposeC

Psychological studies show that some people are quick-tempered .
A. at heart
B. on purpose
C. in person
D. by nature

A. at heartB. on purposeC. in person(答案→)D. by nature解析：　by nature 天生，生来。in person 1）亲自，亲身：I shall be present at the meeting in person.(我将亲自出席会议。)2）身体上，外貌上：In person he was handsome, strong and healthy.(他面目清秀，体格强壮。)at heart 1)内心里，实质上：His manners are cold, but he is at heart a kind man. (他的言谈举止有些冷淡，但实际上他是一个好心肠的人。)2）考虑的是......：When I say don't eat sweets, I have your health at heart.(我叫你别吃果糖，是考虑到你的健康。)on purpose 故意地。

这个答案应该是对的