#### Answer

$2$;
$0 \text{ and } 1$

#### Work Step by Step

The numeral $1101_{\text{two}}$ has a base of $2$.
The digit symbols are the counting numbers less than the base $2$.
Thus, the digit symbols are $0, 1$.
Therefore, the missing expressions in the given statement (in order) are:
$2$;
$0 \text{ and } 1$