The GCD of given numbers is 1.
Step 1 : Find prime factorization of each number.
$$\begin{aligned}16 =& 2\cdot2\cdot2\cdot2\\[8pt]28 =& 2\cdot2\cdot7\\[8pt]32 =& 2\cdot2\cdot2\cdot2\cdot2\\[8pt]37 =& 37\\[8pt]45 =& 3\cdot3\cdot5\\[8pt]1 =& 1~~~ \color{gray}{\text{ (1 is prime)}} \\[8pt]11 =& 11\\[8pt]\end{aligned}$$(view steps on how to factor 16, 28, 32, 37, 45, 1 and 11. )
Step 2 : Put a box around factors that are common for all numbers:
$$\begin{aligned}16 =& 2\cdot2\cdot2\cdot2\\[8pt]28 =& 2\cdot2\cdot7\\[8pt]32 =& 2\cdot2\cdot2\cdot2\cdot2\\[8pt]37 =& 37\\[8pt]45 =& 3\cdot3\cdot5\\[8pt]1 =& 1\\[8pt]11 =& 11\\[8pt]\end{aligned}$$Note that in this example numbers do not have any common factors.
Step 3 : Multiply the boxed numbers together:
Since there is no boxed numbers we conclude that $~\color{blue}{ \text{GCD = 1} } $.