The correct answer is option B that is, transmitting electron microscope.
The core organelles comprise the mitochondria, nucleus, endoplasmic reticulum, and various others. The microscopes play an essential function in understanding organelles.
Although the majority of the organelles are not clearly observed with the help of light microscopy, and those that can be seen like nucleus are not studied in detail, as their size comes nears to the resolution limit of the light microscope. The complete composition of organelles had only become clear after the discovery of a transmission electron microscope.
