Which occurred before nucleosynthesis began? check all that apply. universe became transparent quarks started to form inflationary expansion occurred electrons started to form stars were born

Electrons started to form and Stars were born occurred before nucleosynthesis began. Nucleosynthesis is the method that generates new atomic nuclei from pre-existing protons and neutrons.

Therefore, before nucleosynthesis electrons started to form and stars were born for the formation, of new atomic particles for further processes.

Quarks started to form

Inflationary expansion occurred

Electrons started to form

Explanation:

Nucleosynthesis is in the process before a star is born so D is incorrect.  The universe became transparent is just a silly answer so A is incorrect.

c. heat from the poles back down towards the equator.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.