The correct option is B 160-180 mg/100 ml
The proximal tubule can only reabsorb a limited amount of glucose. When the blood glucose level exceeds about 160-180 mg/dl or 160-180 mg/100ml, the proximal tubule becomes overwhelmed and begins to excrete glucose in the urine. this point is called the renal threshold of glucose (RTG).
So, the correct answer is option B.