Final answer:
The true statement about Ohio's speed limits is (D) Outside business districts, the speed limit on urban state routes other than controlled-access highways is 35 mph except where otherwise posted.
Step-by-step explanation:
The correct statement about Ohio's speed limits is: (D) Outside business districts, the speed limit on urban state routes other than controlled-access highways is 35 mph except where otherwise posted. It is important to note that in Ohio, the maximum speed limit on freeways within municipal corporations is not 75 mph as mentioned in option (A), making that statement false.
Regarding option (B), under adverse conditions, drivers are expected to adjust their speed for safety and not necessarily adhere to the posted speed limit, hence that statement is also incorrect. For option (C), the speed limit in urban alleys is typically lower than 35 mph, so this statement is not true either. Therefore, speed limits can vary, but drivers must adhere to the specific limits posted or the general speed limits applicable where signs are not present.