Along with the nineteenth-century landscape paintings that depict fact

There are two strategy to crack this.
1.
"industrialization damaged agricultural economies" is subject-verb clause. needs to be succeded by "that". Eliminate B, D & E
A is too wordy than C. Option C conveys clear meaning.

2.
Selection of idiom between "Seem to" and "Seem like". In contex with above sentence I prefer "Seem to".

IMO C

Along with the nineteenth-century landscape paintings that depict factories encroaching on fields, Thomas Hardy’s novels seem like they is suggestive that industrialization damaged agricultural economies, marring the landscape and destroying people’s livelihoods.

A. like they is suggestive that -> "they is" incorrect.
B. as if to suggest -> "as if" is correct. But, we need comma or something to get to "not underlined sentence part"
C. to suggest that -> to suggest that industrialization did x ,y and z...It is correct.
D. suggestive of -> "suggestive of" is incorrect.
E. like a suggestion of-> Suggestion is a noun and follows by "seem". For noun clause to use, we need "to be". Incorrect.

So, I think C.

Along with the nineteenth-century landscape paintings that depict factories encroaching on fields, Thomas Hardy’s novels seem like they is suggestive that industrialization damaged agricultural economies, marring the landscape and destroying people’s livelihoods.

A. like they is suggestive that Incorrect

they is redundant, suggestive is wrong

B. as if to suggest Incorrect

as if uses wrong

C. to suggest that Correct

D. suggestive of Incorrect

suggestive of wrong

E. like a suggestion of Incorrect

of uses wrong, that require

Ans: C

Analysis:
Along with the nineteenth-century landscape paintings
Thomas Hardy’s novels
In the above statement 'Novels' is the subject of the sentence.

seem like / seem to
Seem like meaning appear like , seem to means give the impression of

Here seem to is the correct usage. We can eliminate A and E based on this.

A. like they is suggestive that - Eliminate based on our analysis - INCORRECT
B. as if to suggest - 'As if' is redundant, GMAT always likes Concise answers - INCORRECT
C. to suggest that - Concise and conveys correct meaning. - CORRECT
D. suggestive of - Seem suggestive changes the intended meaning. - INCORRECT
E. like a suggestion of INCORRECT