The rates show changes in shares of revenue. They do not establish production efficiency, staffing actions, or whether a change will last.
The lower gross margin leaves less after cost of revenue per sales dollar. The higher operating margin means the operating-expense share fell enough to more than offset that change. The rates do not identify a cause.
A reclassification could change gross margin without changing operating margin, but the rates alone do not establish that it happened.
The rates describe different parts of the statement. A higher operating margin does not erase the gross-margin change or prove its cause.
Answer: b
The rates show a larger cost-of-revenue share and a smaller operating-expense share of revenue. They do not identify the business or accounting cause.