Please solve the following sums:

1. Additive inverse of −42 is:
(a) −42     (b) 42     (c) 0     (d) 1

2. Closure Property does not hold in integers for
(a) multiplication       (b) division       (c)addition       (d) subtraction

3. 0+(−6) is equal to
(a) −6       (b) 0       (c) not defined       (d) none of these

4. Sum of two integer which is negative is always
(a) negative       (b) positive       (c) not defined       (d) none