1. On a highway, starting from $3 \mathrm{~km}$, a speed limit sign is encountered every $4 \mathrm{~km}$, and starting from $10 \mathrm{~km}$, a speed monitoring device is encountered every $9 \mathrm{~km}$. If a car first encounters both facilities simultaneously at $19 \mathrm{~km}$, then the kilometer number where it encounters both facilities for the second time is ( ).
(A) 36
(B) 37
(C) 55
(D) 90
-.1.C.
Since the least common multiple of 4 and 9 is $36, 19+36=55$, therefore, the second time they pass both facilities simultaneously is at $55 \mathrm{~km}$.