Q:

むやみに equivalents : 勝手に vs よく考えないで

Working on practice problems for JLPT N1,
had the following sentence:
むやみに　知らない人に話しかけないほうがいい。
Correct answer per the book is よく考えないで.
Incorrect answer per the book 勝手に
Can someone tell me why the former is to be preferred?

A:

There's a bit of a nuanced difference there.

勝手に is acting without caring about (the effect on) others.
むやみに however is acting without thinking about the consequences.

So, the answer よく考えないで matches むやみに's meaning of doing something without considering if it might (e.g.) inconvenience others. In contrast, using 勝手に would mean doing it without caring if it inconveniences others.
EDIT: would be nice if you explain what I"m getting wrong when you downvote.

