What should the scientist do to best gain scientific understanding of this topic? Analyze the results, and change the experimental methods to retest the hypotheses in a different way.
Discard the faulty results that do not support the original hypothesis, and repeat the experiment using the same methods.
Analyze the procedural errors that took place in the experiment, and summarize these in a conclusion statement.
Repeat the experiment and adjust new data to support the original hypothesis.

The correct answer would be - Analyze the results and change the experimental methods to retest the hypotheses in a different way.

Explanation:

In a scientific investigation or experiment, if there is an unexpected result during testing a hypothesis. A Scientist must analyze the procedure and result to find the possible explanation or errors that led to a particular result.

After analyzing and finding what must have happened scientists need to do changes in the experiment setting or method and retest the hypothesis in a different way to a better understanding of the topic.

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds