The silent student may be shy or insecure or may not want to standout as a brain. In some situations being a brain makes you an outsider and left out of activities.

The classes that I teach are mostly studio (design) lab classes and the students are involved in individual projects. Most of the questions are related to individual projects. Redirection about the question to get them to look at the design process and come up with the answer themselves seems to work best. If it is applicable to all the students - I do what I call a teachable moment and involve all of the students in the process.