please answer following questions, the first part is correct.

Consider the helix r(t) = (cos(-2t), sin(-2t), 2t). Compute, at t = : A. The unit tangent vector T = ( -sqrt(3)/sqrt(i -1/sqrt(8) 2/sqrt(8) B. The unit normal vector N = ( C. The unit binormal vector B = ( D. The curvature K =