Sets

To solve this problem, we need to find the difference between the sets and , denoted as .

1. Given Sets:

2. Finding :
The set difference consists of elements in that are not in .
Looking at both sets, the only element present in but not in is .

3. Conclusion:

Final Answer:
The correct option is (B)

To solve the problem, we need to find the intersection of the sets , , and . The intersection of sets refers to the elements that are common to all the sets.

1. Given Sets:
- Set
- Set
- Set

2. Find the Intersection :
The intersection of the sets , , and consists of the elements that are present in all three sets.
- contains only .
- contains and .
- contains , , and .
The common element in all three sets is . Therefore, .

Final Answer:
The correct answer is option (A): \{a}\.

To solve the problem, we need to find the difference of two sets, denoted as . This means we list the elements that are in set B but not in set A.

1. Write down the elements of each set:
Set A = {C, O, V, I, D, 19, 2020}
Set B = {C, O, V, I, D, 19, 2021}

2. Understand Set Difference :
This operation results in the elements that are in B but not in A.

3. Compare B and A:
All elements in B are present in A except for one element:
- 2020 is in A but not in B
- 2021 is in B but not in A

4. Determine the Difference:
The only element in B that is not in A is 2021.

Final Answer:
The correct answer is option (B): {2021}.

To solve the problem, we need to identify the correct statement related to the null set (empty set).

1. Understanding the Symbols:
- denotes the null set (an empty set with no elements).
- denotes the number of elements in the set .

2. Analyzing Each Option:
(1) → Incorrect, because is a set, not a number.
(2) → Correct, because the number of elements in the null set is 0.
(3) → Incorrect, because is an empty set, but is a set containing one element: 0.
(4) → Incorrect, as usually refers to the complement of , which is not defined without a universal set.

Final Answer:
The correct statement is .