Public lice, i think that is the one because it can be spread by sharing combs, contact by long hair, and many other scenarios.
Your answer to this statement will be A. conjugation
After some research I found the important parts mostly bolded
Advantages:
1) Although the technology at first seems like something done for convenience rather than being something of significant utility, the fact is that poorly developed nations like India which have a relatively poor vaccination program are most likely to benefit from such a vaccine.
This is also the reason why many of the projects mentioned here (including Arntzen's early work) have been funded by the WHO.
2) Mucosal immunity : The vaccines which are given parenterally (e.g. Intramuscularly) induce a systemic response but little or no local immune response in the GI tract. This so called "mucosal immunity " is increasingly being considered very important for defense against GI pathogens. ( Remember OPV..)
3) And of course, it's painless and convenient
Disadvantages:
1) The vaccine dose would be inadequate if the patient eats only one banana/potato instead of the recommended two. Furthermore, there might be difficulties in judging the dose itself since the amount of antigen in each fruit cannot be accurately measured.
2) The risk of introducing a new gene into the Plant DNA population is not known. The gene may jump species and propagate into other plants (or wild varieties of the same plants).
This may cause unpredictable results including a decrease in the number or even extinction of a particular plant species due to growth stunting caused by the viral/bacterial gene. (This has been known to occur in research studies, including Arntzen's)
3)"Oral Tolerance": In another concern, scientists need to be sure that vaccines meant to enhance immune responses do not backfire and suppress immunity instead. Research into a phenomenon called oral tolerance has shown that ingesting certain proteins can at times cause the body to shut down its responses to those proteins.
This may cause the body to become more susceptible to a particular disease agent rather than become immunized against it.
Provide individualized physical education instruction or services to children, youth, or adults with exceptional physical needs due to gross motor developmental delays or other impairments.
TLDR: they work with people who have developmental issues one on one
