Why group Pauli observables before measurement?

Question: In VQE or Hamiltonian expectation estimation, why are Pauli terms often grouped before measurement? A) To make all Hamiltonians diagonal in the computational basis B) To avoid using ansatz circuits C) To remove the need for classical optimization D) To reduce measurement overhead by measuring compatible observables together Correct: D Explanation: Hamiltonians are often expressed as sums of Pauli strings. Compatible or commuting terms can sometimes be measured together, reducing the total number of distinct measurement circuits needed. Topic: quantum computing / VQE / measurement optimization