Step 1: Understanding the Concept
Each hormone has a typical function, and the pairs given must be checked one by one.
Step 2: Check the pairs
Oxytocin causes uterine contractions at birth, so it is the birth hormone.
Aldosterone makes kidney tubules retain sodium, so it is the salt-retaining hormone.
Progesterone maintains the uterine lining and pregnancy.
Step 3: Find the mismatch
Calcitonin lowers blood calcium, so it is hypocalcaemic. The hypercalcaemic hormone is parathormone, so option (C) is mismatched.
Final Answer:
The mismatched pair is Hypercalcaemic hormone - Calcitonin.
\[ \boxed{\text{(C) }\text{Hypercalcaemic hormone - Calcitonin}} \]