若选拔优秀毕业生的条件是：年龄（age）小于19岁，三门功课总分(total)大于2

age<19 and total>285 and mark1=100 or mark2=100 or mark3=100

age<19 and total>285 or mark1=100 or mark2=100 or mark3=100

age<19 and total>285 and （mark1=100 or mark2=100 or mark3=100）

(age<19 or total >285) and (mark1=100 or mark2=100 or mark3=100)