Why is the having of chromosomes essential for sexual reproduction?

Which of the following is a possible reason for sleep? a) growth b)digestive c)speed d)intelligence

Check all that apply diatoms are marine algae that have a shell made of silica, what are some of the uses of the silica shell after the diatoms die? 1.the shells make up the diatomaceous earth used in filters 2.it can be used as an ingredient in abrasives 3.they are used in food products 4.the shells can be used in some insulating materials

The activity of the modern sample is 1.10 bq . how long does that measurement take?