Pulsars a. spin very rapidly when they're young. b. are the cause of gamma-ray bursts. c. spin very slowly when they're young, and gradually spin faster as they age. d. generally form from 25-solar-mass stars. e. emit radio in all directions.

A. spin very rapidly when they're young.

Explanation:

A pulsar (pulsating star) is a neutron star that emits very intense jets of electromagnetic radiation in the range of radio waves, X-rays or gamma rays, at short and periodic intervals due to its intense magnetic field that induces this emission.  

One of its main charateristics is its  rapidly rotation (spin) when this star is young. So, as the star spins, beams of radio radiation from it sweep through space. If one of these beams points toward the Earth, we observe a pulse.  

This is possible when the magnetic pole of the star "points" to the Earth and then stops pointing a thousandth of a second later due to the fast rotation of the star, appearing again when the same pole returns to point towards Earth.  

  1.the balanced   chemical equation is as below

cu +   2 ag(no)₃ → cu(no₃)₂   +2 ag

2.the   much silver   produced   is   50.9 g

step 1: find the   moles of cu

moles =   mass÷   molar mass

  from periodic table the molar mass of cu = 63.5 g/mol

moles is therefore = 15.00 g÷ 63.5 g/mol = 0.236   moles

step 2: use the mole ratio to determine the   moles of ag

from equation above   cu: ag   is 1: 2

therefore the moles of ag   =0.236   moles   x 2/1 =0.472   moles

step 3: find the mass   of ag

mass = moles x molar mass

from periodic table   the molar mass of ag =107.87 g/mol

mass   = 0.472   moles x 107.87 g/mol = 50.9 g

3.   the   much   silver   collected worth is   1.797 oz

  convert   50.9 g   to oz

that is   1 gram = 0.0353 oz

          50.9 grams =?   oz

by cross multiplication

={(50.9 grams x 0.0353 oz) / 1   gram}   =1.797 oz

i think the answer is a, hope this : )