Answer: Pretty sure the answer is C
Step-by-step explanation:
0.9. The reason why is because the 5 brings the 8 to a 9.
Given that the half life of 3H is 12.3 years.
The amount of substance left of a radioactive substance with half life of

after t years is given by

Therefore, the number of years it will take for 18% of the original tritinum to remain is given by

Therefore, the number of <span>years that the time could be read at night is 30.4 years.</span>