I would go with the first because of "serious".
Student or Learner
Please check. "This is a serious matter that needs to be thought about" or "can be thought about".
I prefer a noun rather than a new verb -- This serious matter really needs some thought.
So, according to you. Second one is also exceptable however it is not preferred(I hope sentence is correct).
Would it be acceptable if 'can' was replaced with 'must'?
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.