The correct answer is: Blocking
Rationale: Blocking (or difficulty stating) is where members put obstacles in the way of proposals: this may be a positive contribution in circumstances where the proposals are risky or unrealistic - but it is probably contributing to the problem here.
Bringing-in is encouraging the contribution of others; summarising, drawing together passages of discussion; testing understanding, checking whether points have been understood. They are generally supportive behaviours, which could be used to get the team back into constructive discussion.
