Which expression is equivalent to a3−1a2−1÷a2+a+1a+1\frac{a^3 - 1}{a^2 - 1} \div \frac{a^2 + a + 1}{a + 1}a2−1a3−1÷a+1a2+a+1?
1
a−1a-1a−1
a−1a+1\frac{a-1}{a+1}a+1a−1
1a−1\frac{1}{a-1}a−11