sequence of answering

hello every one...

i want to know is it

Mandatory to answer the question in a particular pattern like if 1^st question consists of two bits say 1(a), 1(b) and 2^nd question also consists of two bits 2(a), 2(b). Eg take LAW paper.

Now I want to know whether can we answer the questions in the following pattern

2(b)

1(a)

2(a) etc,,

thanks ....