Step 1: Understanding the comparative structure.
In Spanish, to compare equality in adjectives or adverbs, we use the structure tan + adjective/adverb + como.
Step 2: Apply the rule.
Here, we compare Luisa’s level of sympathy to what the speaker thought. The adjective “simpática” requires “tan” before it and “como” after it.
Correct form: “Luisa no es tan simpática como yo pensaba.”
Step 3: Analysis of options.
- (1) tal, cuanto → Incorrect; does not form a comparative.
- (2) tanto, como → Used with nouns, not adjectives.
- (3) tal, cuando → Incorrect combination.
- (4) tan, como → Correct; forms a comparison of equality.
Step 4: Conclusion.
Thus, the correct answer is tan, como.