Indicate the number of each noun in italics in the following sentences and state whether the noun has the corresponding singular or plural form:
1. The sheep were spread all over the field. (The sheep)

2. He could see the trout moving among the stones. (the trout)

3. The table was covered with fruits. (The table)

4. He took off his glasses and cleaned them. (glasses)

5. They left in twos and threes. (twos)

6. The young man was studying mathematics. (mathematics)

7. The house was on the outskirts of the town. (the outskirts)

8. The signboard was thirty-five feet long. (feet)

9. There were unusual phenomena. (phenomena)

10. A series of paintings were hanging on the walls. (A series)

11. He was standing among the lookers-on. (lookers-on)

12. Here is your bill: twenty-four pounds ten pence. (pounds)

13. 'The Origin of Species' gave Darwin an acknowledged place among the greatest men of science. (science)