AC ≅ AC and Hypotenuse -Leg (HL) are the missing items in the blanks.
Conditions for congruency of triangles.
Two triangles are congruent if their corresponding sides and angles are equal.
If the hypotenuse and one leg of a right-angled triangle are proven to be equal to the corresponding parts of another right-angled triangle, the triangles are congruent.
From the figure provided
Statements(Reasons)
∆ABC and ∆CDA are right ∆s; AD ≅ CB(Given)
AC ≅ AC (Reflective property of ≅)
∆ABC ≅ ∆CDA (Hypotenuse -Leg (HL).
AC ≅ AC and Hypotenuse -Leg (HL) are the missing items in the blanks.
Other criteria that can be used include Side-angle-side, Side-Side-Side, Angle-Side-Angle and Angle-Angle-Side depending on the given information.