Who observed the "mitochondria" first?

The cristae of mitochondria possess:

Identify the parts highlighted as $A$ and $B$ and explain why they are called semiautonomous organelles.

How many organelles of a eukaryotic cell are considered to have had an independent existence during the early events of evolution?

Which structure is/are considered as semi-autonomous organelle?

Identify the $X, Y$ and $Z$ parts from the given figure of a mitochondrion: