What is the group of compactly arranged homogeneous cells located at the center of each microsporangium in a young anther called?

The pollen grain represents

Given below are two statements.
Statement $I$: Generally,anthers in angiosperms are dithecous,having two pollen sacs in each lobe.
Statement $II$: Each sporangium produces pollens from sporogenous tissues by the process of sporogenesis.
In light of the above statements,select the correct answer from the options given below.

Isobilateral tetrads are commonly found in........

Pollen grain develops from . . . . . . of anther.

The type of fossil pollen grains present in the area may be helpful in the exploration of