The sum of the digits of a two-digit number is $9.$ If the digit in tens place is twice the digit in the units place, then the number is:

The correct option is B: $63$

Let the digit in the unit's place be $x$.

According to the question, the digit in the tens place is $2x$.

It is given that sum of digits is $9.$

$2x+x=9$

$\Rightarrow 3x=9$

$\Rightarrow x=3$

Digit at ones place $=3$

Digit at tens place $=2\times 3=6$

Thus, the number is $63.$