How many of the following pairs of terms are like terms?  ($1$) $2$ and $6$;~($2$) $-2a$ and $-2c$;~($3$) $78x$ and $-200x$;~($4$) $8$ and $y$;~($5$) $4ab$ and $4b$ 
选项为:A:$$1$$  B:$$2$$  C:$$3$$  D:$$4$$  请回答其中一个选项.