There’s 4; guanine, adenine, cytosine, and thymine (or uracil rather than thymine if it’s an RNA working copy)
For this problem, taking into consideration the options presented with it, the most probable and the most likely answer to this would be the third one which is a virus.
Well, viruses and bacteria and other pathogens would cause foodborne illnesses. That would be common sense. The thing is, in the presented options, poor personal hygiene is a very strong option that could overthrow the third one. Poor personal hygiene doesn't only speak to the person's under care of his own body, but also speaks to how food is handled. Overall, a virus would be the biggest cause for this. If the food that is stricken with a virus is eaten by a person with exemplary hygiene, then that person would become ill, the same as a person that has poor personal hygiene.
There are 2 types of transport mechanisms that involve the movement of materials across the cellular membrane:
1. Passive Transport Mechanisms which is the movement of materials that does not require energy. Instead the movement relies on the permeability of the cell. Under this are three kinds of passive transport mechanisms:
a. Simple Diffusion:
- the movement of materials from a region of higher concentration to lower concentration. No external energy is necessary for the movement. The materials supply the energy themselves.
b. Facilitated Diffusion:
- This differs from simple diffusion because the movement is facilitated by proteins that make up the structure of the membrane. The proteins include channel proteins that allow ions and smaller molecules to cross the membrane. The other protein are the carrier proteins, which bind to materials like sugar molecules and move it across the membrane.
c. Osmosis:
- This is the diffusion of water across the membrane. Osmosis moves water from regions where there are more water molecules of water per volume to regions where there are less water molecules per volume.
2. Active transport on the other hand is a movement mechanism that requires energy. It uses the energy to send materials against the direction it is coming from through simple diffusion. This mechanism is used in a way to keep unwanted ions or other materials out of the cell.