Answer:
B.
1-3hours
Explanation:
This is because a diabetic patients have increased blood sugar or glucose concentration. After eating a meal, the blood glucose concentration will be increased as it is been accumulated . Therefore it is best diabetic patient exercise at that hour to reduce it's blood glucose concentration.
Double
Explanation:
Since the period T of a pendulum is given by

By increasing the length of the pendulum by 4, the period becomes

You can see that the period doubles when we increase the length by a factor of 4.
A coil of insulated wire around an iron core