The correct option is A.
Step-by-step explanation:
Line A and B are parallel lines.
....(1) (Alternate exterior angles)
(Supplementary angles)
![3x+9x=180](/tpl/images/0335/6266/1a9ed.png)
![12x=180](/tpl/images/0335/6266/77aec.png)
![x=15](/tpl/images/0335/6266/54281.png)
The value of x is 15.
Put this value in equation (1).
![\angle 1=3\times 15=45](/tpl/images/0335/6266/dd23d.png)
Therefore measures of angle 1 is 45° and option A is correct.