5.If Hilda and Irene have telephone duty together on Monday and on Wednesday， which of the following must be true?

　　(A)George and Hilda have telephone duty together on Friday.

　　(B)George and Irene have telephone duty together on Friday.

　　(C)George has telephone duty on exactly three of the days of the week.

　　(D)Hilda has telephone duty on exactly three of the days of the week.

　　(E)Irene has telephone duty on exactly three of the days of the week.

　　6.If George and Hilda have telephone duty together on Monday and George and Irene have telephone duty

together on Friday, any of the following can be true

　　EXCEPT：

　　(A)George and Hilda have telephone duty together on Wednesday.

　　(B)George and Irene have telephone duty together on Wednesday.

　　(C)George has telephone duty for four days of the week.

　　(D)Irene has telephone duty for four days of the week.

　　(E)Hilda and Irene have telephone duty together for two days of the week.

　　7.If there is one pair of employees who have telephone duty together for three of the five days， which of the following must be true?

　　(A)George has telephone duty on Wednesday.

　　(B)George and Hilda have telephone duty together for three days of the week.

　　(C)Hilda and Irene have telephone duty together for three days of the week.

　　(D)One of the three employees has telephone duty for exactly two days of the week.

　　(E)Exactly one of the workers has telephone duty for exactly three days of the week.

　　8.Any of the following can be true EXCEPT：

　　(A)One pair of employees has telephone duty together for exactly one day of the week

　　(B)One pair of employees has telephone duty together for exactly four days of the week

　　(C)The pair of employees that has telephone duty together on Monday also has telephone duty

together on Wednesday

　　(D)The pair of employees that has telephone duty together on Tuesday also has telephone duty

together on Wednesday

　　(E)The pair of employees that has telephone duty　together on Thursday also has telephone duty

together on Friday