Final answer:
The smallest object that can be seen with an electron microscope among the given options is an individual molecule (D). While atoms can be observed using highly specialized electron microscopes, molecules are the correct answer when compared to the other choices.
Step-by-step explanation:
The smallest object that can be seen using an electron microscope is an individual molecule (D). Although electron microscopes are extremely powerful and can image single atoms, for the scope of this question, when comparing the options available, the individual molecule is the correct answer.
Electron microscopy leverages electron waves to see fine details of nano-size objects, allowing us to observe structures that are well below the threshold of visibility via light microscopes or the unaided eye.
Atoms, such as the hydrogen atom (E), can indeed be observed using specialized electron microscopes, but the question asks for the smallest among the given options.
The sophistication of the electron microscope, with its vacuum technology and advanced detectors, enables researchers to examine and understand structures as small as individual molecules, which are larger than individual atoms.