  We study the validity of the Blackadar-Kirchberg conjecture for extensions of
separable, nuclear, quasidiagonal $C^*$-algebras that satisfy the UCT. More
specifically, we show that the conjecture for the extension has an affirmative
answer if the ideal lies in a class of $C^*$-algebras that is closed under
local approximations and contains all separable ASH algebras, as well as
certain classes of simple, unital $C^*$-algebras and crossed products of unital
$C^*$-algebras with the integers.
