Let
Ω
\Omega
be a class of unital C
∗
^*
-algebras such that
Ω
\Omega
is closed under tensoring with matrix algebras and taking unital hereditary C
∗
^*
-subalgebras and such that
t
s
r
(
B
)
=
1
tsr(B)=1
and the Cuntz semigroup Cu
(
B
)
(B)
is almost unperforated for any
B
∈
Ω
B\in \Omega
. Then
A
∈
A\in
TA
Ω
\Omega
for any unital C
∗
^*
-algebra
A
∈
A\in
TA(TA
Ω
)
\Omega )
. As an application, this result can be used to study tracially quasidiagonal C
∗
^*
-algebra extensions of tracial topological rank no more than one.