**Edit:** According to the comment of Andre Henriques I revise the question:


What is an example of a noncommutative unital $C^\star$ algebra $A$, which is not Morita equivalent to a commutative algebra, such that for all unital subalgebra $B$ of $A$, $ K\_{0}(B)$ has $\mathbb{Z}$ as a summand? This question is motivated by [this post](https://mathoverflow.net/questions/169270/topological-k-theory-for-commutative-c-algebras) and the fact that commutative algebras and their matrix algebras satisfies the above property.



A question on K- theory of non commutative $C^\star$ algebra
The question only requires regarding K$\_0$ as an abelian group (it has a natural pre-ordering too), which makes it easy to construct simple (in the technical sense) examples. 


Let $A$ be a simple infinite dimensional unital AF C\*-algebra, whose K$\_0$ group is free (as an abelian group) [*lots* of examples exist; see any basic work on AF algebras]. If $B$ is a unital subalgebra, it is stably finite (as $A$ is stably finite). Hence the image of $K\_0(B)$ in $K\_0(A)$ is nonzero (actually, we knew this anyway, since the free module on one generator over $B$ has nonzero image in K$\_0(A)$). The image of K$\_0(B)$ is a nonzero subgroup of the free abelian group K$\_0(A)$, so is itself free, and thus the map to its image splits. So $\bf Z$ is a direct summand of $K\_0(B)$. [Even though $K\_0(B) \to K\_0(A)$ need not be one to one!]


And a simple infinite-dimensional C\*-algebra is not Morita equivalent to a commutative one.


