Which group of words in the sentence is a prepositional phrase? a mother swan and her signets waddled down the smooth rocks and then jumped in the cool water.
a. down the smooth rocks
b. then jumped
c. the cool water
d. a mother swan and her signets

the answer is subjective. i personally agree with the first answer for this question.

if one isn't strictly talking about objects then the correct answer would be 'my eyes' since according to this riddle i am asleep and in order to answer/open the door i need to open my eyes first of all.

however, if one is specifically looking for an object, then the first thing i would open would be the door

hope this !