A selection pressure relates to all of the things that promote a selection among a species, causing the weaker individuals to be prejudiced and the stronger individuals to be only ones to survive.
A tiger hunting prey is an example of selection pressure, because the individuals that are able to escape will survive, and the ones that are caught will probably die. Therefore, it would select the fittest ones to keep on reproducing. So B is incorrect.
Antibiotics are also an examle of selection pressure, because they select the bacteria. Today we know about several species of bacteria that are antibiotics resistant, and this is possible because the strongest bacteria that may be able to survive the action of antibiotics will continue to spread, and the ones that are killed don't. Therefore, C is incorrect too.
The beginning of an ice age also is an example of selection pressure, because an extreme change in temperature will cause several other extreme changes, and a big portion of the living beings will be extinct as they are not fit to the survival in such an extreme environment. Therefore, D is also incorrect.
A surgery is a technique developed by humans to evade the selection pressure. If a person falls and break their arm in nature, this would be a selection pressure as this person will have trouble to find food and to protect themselves. There is a big chance of some inflamation or infection to take place, which could cause the person to die. But surgery is a way to fix the issue, so this person will not be under the mentioned selection pressure. Surgery, than, is a way to evade selection pressure, is not an example of selection pressure.
Therefore, the correct answer is A. Surgery.