If x + 0 = 0 + x = x, which is rational number, then 0 is called:
(a) identity for addition of rational numbers.
(b) additive inverse of x.
(c) multiplicative inverse of x.
(d) reciprocal of x.
Both x and y are in direct proportion, then 1x and 1y are (a) In indirect proportion (b) In inverse proportion (c) Neither in direct in inverse proportion (d) Sometimes in direct and sometimes in inverse proportion