Find, which of the following sets are empty:
(i)The set of points of intersection of two parallel lines.
(ii) A={x:x∈N and 5< x≤6}
(iii) B={x:x2+4=0,x∈N}
(iv)C={even numbers between 6&10}
(v) D={prime numbers between 7&11}
Note : The set, which has no element in it, is called the empty or null set.
Which of the following collection are sets? Give reasons to support your answer.
The collection of all the counting numbers.