Bohr's atomic model may have not been the accurate atomic model we have in the present, but he helped paved the way for accurate discoveries. His model is also called the planetary model. The nucleus, containing the neutrons and protons are situated at the center of the atom. The electrons are orbiting around the nucleus. The model is illustrated as shown in the attached picture.
Answer: 
Explanation:
Significant figures : The figures in a number which express the value or the magnitude of a quantity to a specific degree of accuracy is known as significant digits.
Rules for significant figures:
Digits from 1 to 9 are always significant and have infinite number of significant figures.
All non-zero numbers are always significant.
All zero’s between integers are always significant.
All zero’s after the decimal point are always significant.
All zero’s preceding the first integers are never significant.
Thus has three significant figures
Explanation:
Formation of crystals starts with formation of ions. After the formation of ions the bond formation takes place between the ions.
Bond making between the ions give rise to formation of cubic unit cell by placing them in such a fashion that it forms a shape of a cube.
These cube are then arranged in a repeated pattern which ultimately leads to the formation of crystals.
Hence, the order of steps:
Step 1 : Formation of ions
Step 2: Formation of ionic bonds
Step 3: Formation of cubes
Step 4: Formation of crystals
The answer to this is A i think.
