What is the private key in RSA?
For private key operations you need at least $n$ (the modulus) and $d$ (the private exponent). The primes $p$ and $q$ let you calculate those – or use some shortcuts for quicker computation – so they also suffice.

In practice RSA keys often include all of those values, to avoid having to compute them as needed and to allow for optimized and unoptimized implementations.


  In 2 - (d)


This would not be enough on its own, but the page actually says that the private key includes the modulus.