According to the social identity theory, which one of our many social identities we adopt depends on:

The logic follows here is:

The social identity theory posits that individuals have multiple social identities based on the groups they belong to, such as nationality, religion, profession, etc. The specific social identity an individual adopts at any given time depends primarily on the context in which they find themselves. The context can include various elements such as the immediate social environment, interactions with others, and the specific situation at hand.

Hence, the correct answer is "Option 3".

Important Points

Context is a broad term that encompasses situational factors and social influences, making it the most encompassing and accurate choice.

1) An individual's mood - While mood can influence behavior, it is not the primary determinant of which social identity is adopted.

2) Social influences - Social influences play a role, but they are part of the broader context.  

4) Situational factors - Situational factors are a key component of context but not the whole picture.