Arule of thumb refers

a. rules everyone follows

b. a set process people follow

c. a general rule most people follow

d. a way to measure growth

C. A general rule most people follow

Step-by-step explanation: A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation.  

plants store their excess carbohydrate in the form of starch so that it could be used as energy source later on. the excess carbohydrate is converted into starch in the plastid i.e. chloroplast & this process occurs in the presence of sunlight. it is an insoluble polymer of glucose which gets stored in cell organelles named as amyloplasts. in some plants, starch is also stored in roots and embryos.