Read the following information and answer the given questions.
To understand the functional relationship between these phases of cell cycle Dr.N.Rao and his research associate Dr.Johnson conducted experiments on cell fusion technique.His researches revealed that the cell cycle is sequential ,unidirectional had controlled by a series of chemical signals.His experiments are considered to be a milestone in the cell cycle studies.This study threw a new hope of ray for the budding scientists to carry out reseraches on cell division.`G_+1:3.5 `hrs,M:1 hr are the stages in a cell cycle which occur in a manner with specific time.
`G_1,S,G_2` stages are collectively called……………?

Options

A. Johnson
B. PN: Rao
C. Maheswari
D. Johnson, Potu Rao