This is a really hard question. If we just take into consideration the SP:
The answer is C @steemit. Given that this is the official project account that delegates and distributes its influence over the platform I won't consider it to be a real whale. Then @bittrex and @blocktrades are exchanges accounts and shouldn't be considered whales.
Then D will be my answer as @hendrikdegrote is a whale.

• https://steemd.com/@hendrikdegrote
• https://steemd.com/@steemit
• https://steemd.com/@bittrex
• https://steemd.com/@blocktrades