Context: Scientists in a laboratory were working with insulin, a protein often used to treat diabetes. They left two identical vials of insulin in different places. This table shows how the temperature of each vial changed over 15minutes.
During this time, thermal energy was transferred from () to ().
A. the surroundings . . . each vial
B. each vial . . . the surroundings
Determine the correct option from the provided choices and reply with its corresponding letter.

A