Answer:
The answer is traditional.
Best answer is "As a result"
"For instance" does not really make sense, since (4) is not an example of an idea in (3). "Specifically" does not make a great deal of sense either, for the same reason. "Furthermore" is tempting, but "as a result is best"
"As a result" establishes the causal relationship between (3) and (4), meaning (3) caused (4). The speaker realizes the memory's power as a result of reflecting on the cheerful daffodils.
