Answer: A
90< x < 180
If x = 90, then the OAB would turn into a right traingle and we will have:
AO = OB = 5
AB = √(√5^2 + √5^2) = 5√2
Perimeter of OAB : 5 + 5 + 5√2 = 5(2+√2) that is a little bit bigger than 17(B)
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If x is a little bit less than 180 (because if x=180, then there won’t be any traingle but two parallel lines:
In this case, OA=OB are still the same size(5) but more the x is, the more the AB would be. So the perimeter is even bigger than when x=90.

In general the perimeter of AOB is 10+AB. The least possible value for AB when 90< x < 180, occurs when x=90 and in this case, perimeter of the triangle is bigger than 17.