Question

in the 1930s, many countries refused to accept jewish refugees because immigration quotas had already been
lowered
changed
revised
filled

Explanation:

To determine the correct word, we analyze the context: countries refused Jewish refugees because immigration quotas were already "filled" (meaning the quota limit was reached, so no more could be accepted). "Lowered" implies a reduction in quota size, "changed" is too vague, "revised" suggests an update, but "filled" fits the idea that the quota (number of allowed immigrants) was already met.

Answer:

filled