Answer:
A) Sample B has more calcium carbonate molecules
Explanation:
M = Molar mass of calcium carbonate = 100.0869 g/mol
= Avogadro's number = 
For the 4.12 g sample
Moles of a substance is given by

Number of molecules is given by

For the 19.37 g sample

Number of molecules is given by


So, sample B has more calcium carbonate molecules.
The ratio of the elements of carbon, oxygen, calcium atoms, ions, has to be same in both the samples otherwise the samples cannot be considered as calcium carbonate. Same is applicable for impurities. If there are impurites then the sample cannot be considered as calcium carbonate.
Answer:
photosphere
Explanation:
photosphere
There are 3 main layers of the Sun that we can see. They are the photosphere, the chromosphere and the corona. Together they make up the "atmosphere" of the Sun. The part of the Sun that glows (and that we see with the naked eye) is called the photosphere
Answer:
B. People live longer than they used to
Explanation:
None of the other answers are correct.
The most likely bond between element X and Iodine would be an ionic, or electrovalent, bond. Iodine has seven electrons in its outer shell, also known as the valence shell. To become perfectly stable, it needs only a single electron from another element. Hence no sharing of electron takes place (usually), which is the condition required for it to be covalent bonding. Hence it's most likely an ionic bonding/