Which word could be substituted for 'querulous' in the following context?

The word "querulous" is used to describe someone who is habitually complaining or expressing dissatisfaction in a whining or petulant manner. In this context, substituting "complaining" accurately captures the essence of what "querulous" conveys. It suggests a tone of discontent or annoyance, which aligns perfectly with the nature of the original term.

On the other hand, the other choices do not convey the same meaning. "Happy" implies a positive emotional state, "excited" connotes enthusiasm or eagerness, and "disappointed" suggests a sense of loss or unmet expectations without the ongoing sense of complaint inherent in "querulous." Therefore, "complaining" stands out as the most suitable substitution in this scenario.