Which of the following is the correct syntax for joining tables on more than one column with the ON clause?

table$\_$a AS a JOIN table$\_$b AS b ON a$.$col$1$ AND a$.$col$2=$ b$.$col$1$ AND b$.$col$2$

table$\_$a AS a JOIN table$\_$b AS b ON $($a$.$col$1,$ a$.$col$2)=($b$.$col$1,$ b$.$col$2)$

table$\_$a AS a JOIN table$\_$b AS b ON a$.$col$1=$ b$.$col$1$ AND ON a$.$col$2=$ b$.$col$2$

table$\_$a AS a JOIN table$\_$b AS b ON a$.$col$1=$ b$.$col$1$ AND a$.$col$2=$ b$.$col$2$