Depending on the references, it seems that:
- Either cryptography and steganography are two separate techniques,
- Or that cryptography is a superset covering encryption and steganography.
In you question you link to Wikipedia's steganography page which seems to go toward the first possibility. However, on its side, Wikipedia's cryptography page seems to toward the second one:
Cryptography or cryptology; from Greek κρυπτός kryptós, "hidden, secret"; and γράφειν graphein, "writing", or -λογία -logia, "study", respectively is the practice and study of techniques for secure communication in the presence of third parties called adversaries. [...] Cryptography prior to the modern age was effectively synonymous with encryption, the conversion of information from a readable state to apparent nonsense.
Cryptography is a mean to hide information, and is not to be taken as a synonymous of encryption anymore.
But latter the same page pushes the discussion further by linking to RFC 2828, "Internet Security Glossary", which goes for the first possibility, clearly stating that steganography "is different than cryptography" and introduces cryptology as a superset which "sometimes is said to include steganography".
So, all-in-all, I think that the best answer one can give to your question is that sometimes it is, sometime it isn't. In fact, the more important to remember is that in English language this word may lead to confusion so you need to associate a clear context to it.
Here, you are in the context of an exam, so if this is the official position of the exam authorities regarding this (if there is any, it happens that book preparation authors may involuntary add some confusion by inserting their personal point of view in their book, that's why I prefer to rely at least on two different sources whenever possible for my own studies), you will have no choice but stick with it. Once you have passed the exam, you will be free to tell what made or made not sense in the exam cursus, but first thing first :).