Answer:
The answers are letters B and C.
Explanation:
Their ability to live at several acean depths may be useful to biologists studying deep ocean fish.
Their ablity to capture carbon dioxide may be useful in reducing dlimate change impacts.
These are the two correct because blue algae helps mantain the carbon cycle, which means that algae produces at least half o f the oxygen in Earth's  atmosphere, and it is a seafood, making up the base of aquatic food chains. In adittion, the blue green algae can really reduce greenhouse gases, which can reduce the climate impacts on earth nowadays.