Select the option that will improve the highlighted part of the given sentence. In case no improvement is needed, select 'No improvement required'.
I knew very little Spanish when I came here, but I have been learning and can now make myself understood.

Correct option is C

No improvement required because the sentence is grammatically correct and well-structured.
Explanation:
· The phrase "I knew very little Spanish when I came here" correctly establishes a past action using the past simple tense.
· "But I have been learning" uses the present perfect continuous tense, which is appropriate for describing an ongoing action that started in the past and continues to the present.
· "Can now make myself understood" correctly conveys the result of the learning process.
Example:
✅ I knew very little French when I moved to Paris, but I have been learning and can now communicate well.
Why Other Options Are Incorrect:
· (a) "when I come here, however" – Incorrect, because "come" (present tense) does not match "knew" (past tense).
· (b) "upon arriving here, since" – Incorrect, because "since" implies an action that continues from a specific point in time, which does not fit well here.
· (d) "as soon as I came here, but" – Incorrect, because "as soon as" suggests an immediate action, which does not align well with the sentence structure.