The old man            lonely at all since we began to visit him once a week.       [ ]

A. hasn't felt        

B. don't feel          

C. didn't feel        

D. haven't felt

假设一类土建工程，企业管理费全员人均年开支额是2500元，生产工人占全员80%，人工费占直接工程费比例为12%，全年有效施工天数为240天，日均人工工资单价为20元，则一类土建工程的企业管理费费率为（）。

A.7.8%

B.6.25%

C.52.1%

D.65.1%