A student was observing slides of cell division. In one of the slides, he noticed loosely coiled chromatin depicting DNA duplication. Which phase of the cell cycle could it be?

A.
S phase
B.
Metaphase
C.
M phase

A. S phase

Explanation:

The cell cycle involves all the series of division events that occurs to an organism. Cell division, which can be meiosis or mitosis, involves two main stages viz: Interphase and M phase.

Interphase describes the resting stage of the cell i.e. when the cell is not dividing. The cell uses this time to prepare itself for the next round of division. Interphase stage further consists of three main phases viz: G1, S and G2 phases.

In the S phase or synthesis phase of Interphase, the cell duplicates its genetic material (DNA). Hence, an onion cell observed by a student to have loosely coiled chromatin depicting DNA duplication is in the S-PHASE.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".

c. earths continental crust is thicker than its lithosphere.

because, the lithosphere is the outermost layer of the earth/ 100 km thick and is defined by its machanical properties.the lithosphere contains oceanic and continental crust that varies in age and thickness across locations and geologic time. the lithosphere is the coolest layer of the earth in terms of temperature. the term lithosphere should not be confused with the use of "geosphere" which is used to indicate all of earth systems, including the atmosphere, hydrosphere   and biosphere. the surface of the earth can be divided into the continental crust and the oceanic crust.   the continental crust is made mostly of granite while the oceanic crust is made of basalt. the average thickness of the continental crust is 25 miles and the average thickness of the oceanic crust is 5 miles.   three types of rock, igneous, sedimentary, and metamorphic, make up the surface of the earth. that's why 3 option is preferable.