1.B.three times cheaper than
解析：
1）表示比...大/小几倍 —— 数词 + times + 形容词比较级 + than
如：火车票比飞机票便宜三倍
the train ticket is three times cheaper than the plane ticket
2）表示是...的几倍 —— as + 数词 + times + 形容词原级 + as
如：飞机票是火车票的三倍
the plane ticket is as three times expensive as train ticket.
或者：the train ticket is three times cheap as the plane ticket.
2.D.three times the size of
解析：
1）表示 A 和 B 一样大小 —— A is the size of B
如：这个盒子和那一个一样大
This box is the size of that one
2）表示 A 和 B 的几倍一样大小 —— A is + 倍数（数词+times）+ the size of B
如：尼日利亚是英国的三倍大
Nigeria is three times the size of Great Britain.