For the phrase "for now," is a comma necessary in this sentence? [duplicate]

Question

While practicing for the SAT and doing a practice test, I came across a question where what I believed to be a grammatical mistake in the question (it was missing a comma, I thought) caused me to eliminate that option. However, when I looked back to check my answers, the answer I though was grammatically incorrect was the correct answer. So basically my question is whether or not the option is in fact grammatically incorrect, and if so, does this mean in the future I can't rely on a perceived grammatical mistake to eliminate an option for a question like this? Here is the question (if you are unfamiliar with SAT Writing tests like this, the question is asking what the bolded text should be, from the options given):

Although researchers continue to search for the right combination of factors that will keep fruits fresh and attractive, the problem may be that consumers are overly concerned with superficial qualities rather than the actual freshness of the fruit.

33. The writer wants a conclusion that conveys how the shortcomings of 1-MCP presented in the passage affect the actions of people in the fruit industry. Which choice best accomplishes this goal?

A) NO CHANGE

B) many of the improvements to fruit quality they have discovered so far have required trade-offs in other properties of the fruit.

C) for now many fruit sellers must weigh the relative values of aroma, color, and freshness when deciding whether to use 1-MCP.

D) it must be acknowledged that 1-MCP, despite some inadequacies, has enabled the fruit industry to ship and store fruit in ways that were impossible before.

Correct Answer: C (the one I eliminated because I thought it had a mistake)

My Answer: D

source (refer to this if more context is needed): https://cdn2.hubspot.net/hubfs/360031/PrepScholar-sat-practice-test-3.pdf?t=1524236344173 page 26-26, question 33

Answer 1

After a brief introductory adverbial, a comma is optional and is often omitted:

For now the bulk of their research will necessarily continue to focus on incremental improvements in finding and extracting oil and natural gas.

…but for now the old man with the generous white moustache and the inscrutable gaze is still trying to change the progress of history…

For now the discussion will focus on the sequencing techniques used in inputting both acoustic and electric piano parts.

Other writers choose to use a comma:

For now, the most important element in our developmental equation is your ability to believe in, and effectively argue the case for, these strategic changes.

For now, the deal benefitted only Hunter, and only because Finley was late with a payment.

For now, the agency pays the cost of maintaining the main canal.

Whether you use a comma after introductory For now is your choice. Neither omitting nor retaining the comma is an error in punctuation.