When does human life begin?

e) at a point of "viability" of the fetus (some time in second trimester);

d) at the initial development of the fetus (non-viable; ~ 8 weeks after fertilization; heartbeat often detectable);

a) at the formation of a zygote (sperm fertilizes egg);

b) at the initial development of the blastocyst (~ 5-8 days after fertilization);

c) at the initial development of the embryo (~ 10-12 days after fertilization);

f) at the beginning of the third trimester:

g) at birth. Related question, do you believe it is morally ok to terminate a pregnancy after the point you believe human life begins? Note: In some jurisdictions, "Pregnancy" officially begins at the end of a woman's last menstrual cycle, thus the zygote formation may occur 2 weeks into what they considered a pregnancy.