Main group elements constitute:
A. s- and p- block
B. p- and d- block
C. s- and d- block
D. d- and f- block

Hint:
We can use the knowledge about the basic structure of periodic tables to know about various terminologies related to it. Main group elements are also known as representative elements.

Complete step by step solution
From Dobereiner’s triads to modern periodic table, it took a lot of effort to systematically classify the known elements properly so that all the known elements can fit into it and periodicity of various properties could be explained in a better way.

In the modern periodic table, we have seven rows and eighteen columns that are called periods and groups respectively. The number of periods an element belongs to; represent the principal quantum number for the outermost shell. Similarly, the number of groups an element belongs to; can help us in deducing its electronic configuration of the valence shell. For example, sodium belongs to third period and first group which can be correlated to its electronic configuration:\[{\rm{1}}{{\rm{s}}^{\rm{2}}}{\rm{2}}{{\rm{s}}^{\rm{2}}}{\rm{2}}{{\rm{p}}^{\rm{6}}}{\bf{3}}{{\bf{s}}^{\bf{1}}}\] As we can see the outermost shell is third and it has $1$ valence electron in the $s$ orbital.

Based on the valence orbital, we have divided the eighteen groups into four blocks namely s-block, p-block, d-block and f-block. There are two exceptions to this, ${\rm{H \, and \, He}}$ for ${\rm{H}}$ has been placed separately and ${\rm{He}}$ even though has electronic configuration \[{\rm{1}}{{\rm{s}}^{\rm{2}}}\] is placed in p-block for being a noble gas. The elements in the two blocks, s- and p- are collectively known as main group elements. For these blocks, it is comparatively easier to deduce trends than in the other two blocks.

Hence, the correct option is A.

Note:
We have to have the basic knowledge about the classification of elements and the related terminologies for different bases have been used while defining various terms.