1 Jenny and li Ming get 【on / off 】the train.
2 This sweater is expensiver than that dress. -->
This sweater is more expensive than that dress.
（expensive 是多音节形容词，其比较级需在前面加more构成，而不能直接在词尾加 -er 或 -r构成。）
1 Jenny and li Ming get 【on / off 】the train.
2 This sweater is expensiver than that dress. -->
This sweater is more expensive than that dress.
（expensive 是多音节形容词，其比较级需在前面加more构成，而不能直接在词尾加 -er 或 -r构成。）