Concept:The construction "too ... to" is used to show that something is more than enough, so a result is not possible or not safe.
Explanation:The sentence is: "It was ...... late to go out alone."
We need a word that connects "late" with "to go out alone."
The word "too" forms the pattern "too + adjective + to + verb."
This pattern means "so late that going out alone was not advisable."
For example: "It was too dark to see."
Here, "too dark" stops the action of seeing.
Similarly, "too late" stops the action of going out alone.
"Very late" does not combine with "to go out" to show this meaning.
"Much late" is grammatically incorrect because "much" is not used before a plain adjective like "late."
"So late" normally needs "that" after it, but the sentence has "to go out" instead.
Therefore, the correct option is "too."
Answer: A. too