A0 are the smallest biological structural units of the body.

The correct answer for the blank is-

Cell.

Cell is the smallest biological, structural, and functional unit of all life forms ( such as plants, animals, and bacteria). In other words it is the basic unit of all life forms as all the living organisms are composed of cell.

Cell can exist independently and performs all the cellular processes ( metabolic processes)  that are necessary for the survival.

Thus, cell is the right answer.

answer; i believe is(b)converging

igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

hope this