A is correct.
B's mistake is hard to see, but it is there.
C has no punctuation where it's needed.
D sounds like this: "This shovel is old and rusty it is good enough. However, for the little bit of gardening we do." It sounds rushed in the beginning and the mark doesn't help.
Metaphore is the answer to this one because it’s metaphorically comparing one thing to another
The only word that could potentially be a compound noun is patents, but that has its own definition-a government meeting of some sort.
A compound noun would be a compound word that is also a noun, but there aren't really any compound words.
I know this doesn't really help, sry.