In a "man and nature" knowledge contest, there are 25 questions in the contest. Each question has 4 answers, only one of which is correct, and students are required to choose the correct answer. 4 points are awarded for each correct answer, 2 points will be deducted for not answering or incorrectly answering the question. If a student's score in this competition is not less than 60 points, how many questions must he choose correctly?
在一次"人与自然"知识竞赛中，竞赛试题共有25道题．每道题都给出4个答案，其中只有一个答案正确，要求学生把正确答案选出来．每道题选对得4分，不选或选错倒扣2分．如果一个学生在本次竞赛中的得分要不低于60分，那么，他至少要选对多少道题？
<result>19</result>