Under/over absorption

Good day Sir,

A company uses a blanket overhead absorption rate $5 per direct labour hour. Actual overhead expenditure in a period was as budgeted.
The under/over absorbed overhead account for the period have the following entries:

DR production overhead -$4,000
CR P&L – $4000

Which of the following statement is true?
A. Actual direct labour hours were 800 less than budgeted
B. Actual direct labour hours were 800 more than budgeted
C. Actual direct labour hours were 4,000 less than budgeted
D. Production overhead was over absorbed by $4,000

The correct answer is A.
The debit to the profit or loss account implies that overheads were under absorbed. We are told that actual overhead expenditure was in line with budget, so the only cause of the under absorption has to be actual activity being less than budgeted. A shortfall of 800 direct hours would lead to an under absorption of 800 direct labour hours x $5 per hour =$4,000

Above is the explanation for the answer, but I dun understand.
1) why the p&l in the answer is debit, the question is credit
2) Under absorption not should be actual more than budgeted? why the answer mentioned that actual activity less than budgeted?
3) Why shortfall of 800 direct labour hour will lead to an under absorption