Which good programming practice guideline would make this code easier to read?

DECLARE

v$\_$sal NUMBER$(8,2)$;

BEGIN

SELECT salary INTO v$\_$sal

FROM employees WHERE employee$\_$id $=100$;

UPDATE employees

SET salary $=$ v$\_$sal;

END;

Using a consistent naming convention for variables

Indenting each level of code

Declaring variables using $\%$TYPE

Avoiding implicit data type conversions choose one answer only