Given the task definition and input, reply with output. You are given a short paragraph, a question and two choices to answer from. Choose the correct answer based on the paragraph and write the answer(not the key).

Paragraph: Because these isotopes decay more slowly, they can be used to date much older specimens.
 Question: For dating the age of a fossil, and compared to the isotope Carbon 14 with its 5730 year half-life, would Francium with a 22 minute half-life be a 
 Choices: A)less useful isotope? 
B)more useful isotope
less useful isotope?