Natural numbers are all the counting numbers starting from 1, i.e. {1, 2, 3, ...}
Therefore, statement: '1 is smallest natural number'; is correct.
Whole numbers are all counting numbers and zero, i.e. {0, 1, 2, 3, ...}
Therefore, statement: '1 is smallest whole number'; is wrong.
Integers include the set of natural numbers, their negatives and 0; i.e. {...-3, -2, -1, 0, 1, 2, 3, ...}. Thus, -1 is the greatest negative integer, not the smallest one.
0 is included among integers.
Hence, the statement is correct.