$2$: given the following code;

always @$($posedge clk of negedge nrst$)$

if $(!$nrst $)$ a $=0$;

else if $($b$)$ a $<=0$;

else a $=$ c ;

select all which are true:

A This is not synthesizable

B This is not good practice but is synthesizable

C The code is fine and is synthesizable

D The code needs to include a default value for a