The diagrams show the concentrations of three substances, XXX, YYY, and ZZZ, in the blood before and during a period of intense exercise. One of the substances is glucose and the other two are pancreatic hormones.

Which of the following correctly identifies substances XXX, YYY, and ZZZ?
X = glucagon, Y = insulin, Z = glucose\text{X = glucagon, Y = insulin, Z = glucose}X = glucagon, Y = insulin, Z = glucose
X = insulin, Y = glucagon, Z = glucose\text{X = insulin, Y = glucagon, Z = glucose}X = insulin, Y = glucagon, Z = glucose
X = glucose, Y = insulin, Z = glucagon\text{X = glucose, Y = insulin, Z = glucagon}X = glucose, Y = insulin, Z = glucagon
X = insulin, Y = glucose, Z = glucagon\text{X = insulin, Y = glucose, Z = glucagon}X = insulin, Y = glucose, Z = glucagon