"certificates of deposit are an increasingly popular form of investment, so it is not surprising to see many investors abandoning the securities market for the perceived ‘safe harbor’ of cds. therefore brokers who specialize in stocks will have a more difficult case to make in weeks to come" is which type of argument?

Extended, with at most two conclusions.

Explanation:

In short, an extended argument represents an argument that consists of two or more different sub-arguments. This indicates that you will find conclusions that represent premises for the most important conclusion of the argument. In this case, the main argument is that brokers who specialize in stocks will have a more difficult case to make in weeks to come, and the second argument is that certificates of deposit are an increasingly popular form of investment.

i would say b. research typically uses a variety of sources