3. Arrange the positive integers whose sum of digits is 4 in ascending order. Then 2020 is the ( ) term.
(A) 27
(B) 28
(C) 29
(D) 30
3. B.

Express the number 4 as the sum of no more than four positive integers:
$$
4=1+3=2+2=1+1+2=1+1+1+1 \text {. }
$$

Fill these into a $1 \times 4$ grid, with any unfilled positions filled with 0, to form positive integers no greater than 2020.
Then, $\{4\}$ has 3 ways to fill, $\{1,3\}$ has 9 ways to fill,
$\{2,2\}$ has 5 ways to fill, $\{1,1,2\}$ has 10 ways to fill,
$\{1,1,1,1\}$ has 1 way to fill.
Therefore, the number of integers no greater than 2020 is
$$
3+9+5+10+1=28(\text { numbers })
$$