5. Little Lucas invented his own way to write down negative numbers before he learned the usual way with the minus sign in front. Counting backwards, he would write: $3,2,1,0,00$, $000,0000, \ldots$. What is the result of $000+0000$ in his notation?
A 1
B 00000
C 000000
D 0000000
E 00000000
5. C In Lucas's notation, the first zero represents the minus sign, and the number of other zeroes is the magnitude of the number, so 000 is -2 and 0000 is -3 . Then $000+0000$ is $-2+-3=-5$, which is 000000 in Lucas's notation.