Fill in the blank with the correct word from the options given below:-

She is standing ______________ her husband in this crisis.

The correct option is by.

Detailed Explanation:
The sentence requires a preposition that combines with the verb "standing" to form a phrasal verb that makes contextual sense.
The phrasal verb "stand by (someone)" means to support or remain loyal to someone, especially during a difficult time, trial, or crisis. Therefore, "standing by her husband" correctly expresses that she is supporting him during this crisis.

Let's look at why the other options are incorrect in this context:
• with: While "standing with" can denote solidarity, the established idiomatic phrase for supporting an individual through adversity or a personal crisis is "to stand by" them.
• in: "Standing in" (often followed by "for") means to act as a temporary substitute for someone, which does not fit the context of offering emotional or moral support during a crisis.
• for: "Stand for" means to represent, advocate for a cause, or tolerate something (e.g., "I won't stand for this behavior"), which is not appropriate in this context.

Thus, "by" is the correct word to fill in the blank.