Half-life is ......1...... needed for the ......2...... of a sample of a radioactive isotope to halve. Which words correctly fill gaps 1 and 2?
- A1: half of the time taken; 2: nucleon number of
- B1: half of the time taken; 2: number of nuclei in
- C1: the time taken; 2: nucleon number of
- D1: the time taken; 2: number of nuclei in