REA book review question

[26186514]

on Page 90, sample test 2, problem 62:
Let R be a ring and let x<>0 be a fixed element in R. Which of the followin is a subring of R?
In the choices, there is one {nx|n is an integer}.
I think this is a subring, since rings do not have to be closed under multiplication. However, the answer gives no.
Any idea?

[vonLipwig]

Some people require that a subring contain the multiplicative identity.

[PNT]

Rings do have to be closed under multiplication

[26186514]

oh yes... thanks for the reply. I got it now.