what is the correct way to pass a parameter by reference

a) void Dot(int count) { }

b) void Dot(ref int count) { }

c) void Dot(int count ref) { }

d void ref Dot(int count) { }

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what is the worse-case performance for searching for a value in an array

a) O(N)

b) O(1)

c) O(N^2)

d) O(Log N)