Which of the following sets are empty sets and which are singleton sets ?
(i) Set of even prime numbers
(ii) `{x : x +2 = -1 and x in N}`
(iii) Set months starting with D
(iv) `(x : x " is a common point in two parallel lines")`.

Explanation

To determine which of the given sets are empty sets and which are singleton sets, we will analyze each set one by one.

### Step-by-Step Solution

1. **Set of Even Prime Numbers**:
- The only even prime number is 2.
- Therefore, the set of even prime numbers is {2}.
- Since this set contains one element, it is a **singleton set**.
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