Explanation: Integers are defined as whole numbers (no decimals or fractions are included). Integers include: set of positive numbers {1,2,3,4,.....etc} zero {0} set of negative numbers {-1,-2,-3,-4,....etc}
Now, applying this to the given choices, we will find that the only three whole numbers are 1, -2 and -25. Therefore, these are the only integers.
As for other choices: 2 2/5 is a mixed number (has a fraction), therefore, not an integer 6.78 is a decimal, therefore, not an integer