B. To determine the concavity you must use the second derivative of the function. The second derivative of h(x) is [(x^2)+2]/x^2. Since this can only be positive the function will be concave up always EXCEPT when x=0 because this is where the function is undefined.
C. To find the tangent line at x=4, you can simply plug in 4 in the h'(x) and this will give you the slope of (7/2) at point (4,-3). You can then find the equation since you have the points and the slope:
y-(-3)=(7/2)(x-4)
y+3=(7x/2)-14
y=(7x/2)-17
D. Because the concavity of the curve is up the tangent line must lie beneath the curve.