| Date | May 2018 | Marks available | 1 | Reference code | 18M.1.HL.TZ1.21 |
| Level | Higher level | Paper | Paper 1 | Time zone | Time zone 1 |
| Command term | Question number | 21 | Adapted from | N/A |
Question
When intense physical activity is anticipated, which factor in the blood will increase the frequency of sinoatrial signals to heart muscle?
A. pH
B. Oxygen level
C. Thyroxin
D. Epinephrine
Markscheme
D
Examiners report
[N/A]
