After a crash, the system needs to be booted into runlevel 1. Which option(s) must be typed at the
LILO prompt to achieve this, assuming that the working kernel image is called ‘linux’?

Answer: linux 1

Explanation:
See http://www.snow.nl/dist/xhtmlc/ch02s02.html
“1” is synonymous with runlevel “S” or “single”