Grammar exercise 1 of 4 语法练习1
Use 跟、对 as “How to use 对 (duì) and 跟 (gēn) as prepositions in Chinese grammar” explains it, through 13 items over 7 of its example sentences: fill the gap where the word was taken out, and put the words of each sentence back in order.
How to use 对 (duì) and 跟 (gēn) as prepositions in Chinese grammar
13 items. Each one you miss comes back later in the same sitting.