Which of the following sets is equal to {1, 2, 3, ...}?
{x | x R, x > 1}
{x | x R, x ≥ 1}
{x | x N, x ≥ 1}
{x | x R, x > 1}
{x | x R, x ≥ 1}
{x | x N, x ≥ 1}