Correct Answer:
B. by
The correct answer is by. The phrase 'enough to get by' is a common English idiom meaning having just enough ability or resources to manage or survive. In the sentence, 'My Arabic is not so good, but it's enough to get ___,' the correct preposition to complete the idiom is 'by'. 'Along', 'up', and 'with' do not form this standard idiomatic expression. Therefore, 'by' is the correct answer.