9. This morning, I saw Mr. Robin and his wife on my way   ------ the flower  shop. 求解?

明白你被夾在主句中"on my way..."騷擾了對句字(理想文法SVO)動詞(saw)後的受詞(Mr X and Mrs. X)後還有"後話"是非常難測是在說誰。

雖然這問題實在是考preposition前置詞或preposition phrase的片語字句用法：

on my way ....? flower shop.

這後話的主角是"你"自己，"I saw Mr. X and his wife"反而是在實際情景中的插曲/節外生支的情況。

你是在去花店途中"遇(見)到Mr.X..."。

途中 = on my way
花店 = ? flower shop.

就算不看可選擇的答案，連接的應該表達"去"花店吧，這樣應該考慮：
a. to = 去 
b. for = 為了/因為
c. from = 由/從
d. with = 配合/連同

早上我遇到羅濱夫媽與我同行到花店

This morning, I saw Mr. Robin and his wife on my way   to he flower  shop.