Answer:
d. conditional formatting
Step-by-step explanation:
The option that would most likely be used to accomplish this would be conditional formatting. This is an option in which, if a condition is met, the cell is given certain format changes. In this scenario, the condition would be if a cell is located in column D, then apply a red background and specific font. This would be automatic throughout the entire document so that if any new cell is created in column D it would automatically be formatted according to the conditional formatting that was used.