Final answer:
The social profile picker in Hootsuite Composer is used to select which social media account to post content from, aiding users in managing multiple accounts.
Step-by-step explanation:
When using the Hootsuite Composer, the purpose of the social profile picker is B) Choose account to post from. The social profile picker is a feature within Hootsuite that allows users to select which of their various social media profiles they wish to use when composing and posting a message. This tool is particularly useful for marketers and social media managers who handle multiple accounts across different platforms and need to tailor their social media posts to different audiences. It is an essential part of the content creation process within Hootsuite, ensuring that the right content is shared on the appropriate platform.