The answer would be (A) Protons
Answer:
Option B
Explanation:
Magnification of Microscope is

Mo= Magnification of objective lens and
Me= magnification of the eyepiece.
Both magnifications( of objective and eyepiece) are inversely proportional to the focal length.
Magnification,

when the focal length is less magnification will be high and when the magnification is the low focal length of the microscope will be more.
Thus. Magnification will increase by decreasing the focal length.
The correct answer is Option B i.e. using shorter focal length
The time needed to form a soil depends on the latitude: in environments characterized by a mild climate, it takes 200-400 years<span> to form 1 cm of soil. in wet tropical areas soil formation is faster, as it takes</span>200 years<span>. in order to accumulate enough substances to make a soil fertile it takes </span>3000 years<span>.
Hope it helps! :-)</span>