7. Two angles are marked on the $3 \times 3$ grid of squares.
Which of the following statements about the angles is correct?
A $\alpha=\beta$
B $2 \alpha+\beta=90$
C $\alpha+\beta=60$
D $2 \beta+\alpha=90$
E $\alpha+\beta=45$
7. B The triangle $P Q R$ is congruent to the triangle $T Q S$ since they are right-angled triangles with sides of length 3 and 2. Hence the angle $P Q R$ is also $\alpha^{\circ}$ and then $\alpha+\beta+\alpha=90$. One can check that the other statements are false.