Consider the following statement, and indicates what the output will be:

$$ vector numbers;

$$ numbers.push$\_$back$(5)$;

$$ numbers.push$\_$back$(10)$;

$$ numbers.push$\_$back$(15)$;

$$ numbers.push$\_$back$(20)$;

$//$ Using an iterator to traverse and modify vector elements

$$ vector::iterator it $=$ numbers.begin$()$;

$$ while $($it $!=$ numbers.end$())\{$

$$ if $(*$it $\%2==0)\{$

$*$it $*=2$; $//$ Double the even numbers

$\}$

$++$it;

$\}$

$//$ Display the modified vector elements

$$ cout $<<$ "Modified vector elements: $"$;

$$ for $($int num : numbers$)\{$

$$ cout $<<$ num $<<""$;

$\}$

a$.$

The output will be: "Modified vector elements: $5101520".$

b$.$

The output will be: "Modified vector elements: $5201540"$

c$.$

The code will not compile due to an error.

d$.$

The output will be: "Modified vector elements: $10203020".$

e$.$

The code will compile and execute, but it will result in a runtime error