Answer:
a
The condensed structural formula for methane is

b
The condensed structural formula for ethane is

c
The condensed structural formula for pentane is
d
The diagram for the structural formula for cyclopropane is shown on the first uploaded image
Explanation:
I would look up the answer
I think it’s I
Iodine has 53 protons and 74 neutrons
Abrasiveness is the most common property found in almost every toothpaste. The abrasiveness of a toothpaste is responsible for whitening action and removal of debris stuck on tooth enamel. The same abrasiveness can worsen the teeth sensitivity by damaging the tooth enamel. Relative Dentin Abrasivity (RDA) is used to measure a toothpaste’s abrasiveness.
Other physical properties considered in a toothpaste are as follows:
· Presence of fluoride
· pH
· Foaming ability
Fluoride is a key ingredient that delivers strength to the tooth enamel and fights to prevent tooth decay and gum diseases. Salt and sodium bicarbonate are some materials commonly found in a regular toothpaste. Make sure that your toothpaste contains a good amount of fluoride content. You can use any toothpaste but ensure that you have an effective toothbrush that can provide optimum oral hygiene.
The answer is selenium which is D