Answer:
I would say that A is your answer.
I think this because you would not need to have any specific number of trees in your yard, but you would need a specific number of things for all of your other options.
Explanation:
You probably wouldn't approximate on how many chairs you put in a kitchen. What if you have a 5-member family and you aproxomate the chair number to 4. that would be useless so B is wrong.
C is wrong because you are only getting 1 barbaque. no approximation is nessisary for one item.
D is certainly wrong because you wouldn't want to leave out a uniform, that would mean one member of the basketball team may not get one.