A maternal condition defined by the progressive dilation and effacement of the cervix that begins after 20 weeks and before term (the 37th week of pregnancy). This condition occurs because risk factors that are known or unknown cause uterine contractions and the cervix to dilate and efface prior to the time that the fetus is considered Term or 37-41 weeks. Many known and unknown causes for the condition exist. This condition is the leading cause of morbidity and mortality of newborns.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.

b is the answer and if you need further with anything message me

answerhomologous structures;