Final answer:
The correct sentence is 'Dr. Donnelly is excited to conduct the experiment.' because 'to' is the proper preposition used with 'conduct' in this context. Also, the right statement about a hypothesis is that it must be able to be validated by scientific experiments.
Step-by-step explanation:
The correct sentence is d) "Dr. Donnelly is excited to conduct the experiment." In this context, the word to is used as an infinitive marker before the verb conduct, which indicates what Dr. Donnelly is excited about doing. The other options a), b), and c) use prepositions that are not typically paired with the verb conduct in this manner.
In regard to the second question about scientific hypotheses, the correct statement is a. The hypothesis must be validated by scientific experiments. It means that a hypothesis should be testable and possible to prove wrong or right through experiments or observations.
Some misconceptions might arise from thinking that a hypothesis must be universal or overly concise, but its main purpose is to be testable and explanatory for a phenomenon under study.