I have to agree with the others.
I knew I had to make an assumption about being in the sysadmin role or not. I normally try to avoid assumptions - but when I have to make them, I tend to go with the most likely.
From the question text, membership of sysadmin was unlikely. Not just because of the sp_addrolemember, but also because the best practice of creating specific logins to adminster specific databases is normally used to ensure that people can do their job without the sledgehammer access level of sysadmin.
It would have been a good question if (1) the sysadmin role membership had been included in the question text, and (2) the answer would have included a link to a resource describing the behaviour. (To my surprise, the Books Online CREATE TABLE page does not mention anything on how the default schema for the new table is resolvedO))
PS: Best practise = never rely on default rules for schema, always explicitly include it.