Uranium-235 undergoes fission to produce two neutrons per fission event. if a neutron-absorbing material is mixed in with this sample so that the rate of neutron production drops down to 0.5 neutrons per fission event, which of the following will be effective at achieving a critical mass? check all that apply. surround the sample with a deflective material to prevent neutrons from escaping to the surroundings. add more absorbent material. compress the uranium-235 sample.

The answers that apply;

Compressing the uranium sample ensures that the few neutrons emitted per fusion event, have a higher probability of hitting another uranium atom.

The neutron that manages to pass through the sample without hitting a uranium atom to continue to the fusion chain reaction is deflected by the deflective material back to the sample hence doubling it the probability of colliding with a uranium atom.

the element that provides strength to the exoskeletons of clams and oysters is phosphorus.

this is so because calcium carbonate is the main component in the shells. calcium carbonate is strengthened by phosphorus.

explanation:

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.