Which one of the following functions is monotonically increasing in its domain?

• Correct answer
  A

  $f(x)=\log (1+x)-x+\frac{x^2}{2}$
• B

  $g(x)=2 \operatorname{Tan}^{-1} x-x-1$
• C

  $h(x)=4 \cos x+x$
• D

  $u(x)=\log (1+x)-\frac{x}{x+1}$

Hence, the correct answer is option: 'A'.