Consider the following transfer functions:
$$\eqalign{ & 1.\,\frac{1}{{j\omega + 1}} \cr & 2.\,\frac{1}{{{{\left( {j\omega + 1} \right)}^2}}} \cr & 3.\,\frac{1}{{\left( {j\omega + 1} \right)\left( {j\omega + 2} \right)}} \cr} $$
The transfer functions which have a non linear phase are:

A. 1 and 2 only

B. 1 and 3 only

C. 2 and 3 only

D. 1, 2 and 3

Answer: Option D