The s phase of the cell cycle results in the production of two identical copies of each chromosome, known as

In a cell cycle, the S phase or the synthesis phase is the part in which the DNA (deoxyribonucleic acid) is replicated. This result in doubling the amount of DNA present in a cell.  

This replicated DNA is later condensed to form the chromosome. These chromosomes have two identical copies of DNA bind together with help of a centromere. The identical copies in each chromosome is known as sister chromatids, which get separated at the time of Anaphase.  

Hence, the given blank can be filled with Sister chromatids.  

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explanation:

plate tectonics and volcanic euptions

over time, plate tectonic processes cause continents to move to different positions on the globe.

for example, britain was near to the equator 300 million years ago, and therefore was hotter than it is today. for further details look at our climate through time poster or online map.

the movement of the plates also causes volcanoes and mountains to form and these too can contribute to a change in climate.

mountain ranges formed by plate tectonics. large mountain chains can influence the circulation of air around the globe, and consequently influence the climate.   warm air might be deflected somewhere cooler by the mountains.