It would be easier to answer if I could the poem
pal has been in the business of this invention
Answer:
C: it is dark and treacherous, while the courtyard is hot and sunny.
Explanation:
The least common multiple of 9 and 6 is 18 so in 18 months she will replace the bulb for the 2nd time and the air filter for the 3rd time. It will be the first time they are replaced together.