I think the correct answer would be A. The yolk sac becomes the placenta. It is membranous sac that is attached to the embryo. It provides all the nutrition and the blood cells needed by the embryo. It is also called the umbilical vesicle.
The answer is T, True. Secondary pollutants are pollutants that we do not directly release, but that are created as a side effect of releasing primary pollutants, such as carbon dioxide, sulfur oxides, and particles such as ash and dust. Secondary pollutants include acid rain, ozone, smog, and CFC's (chlorofluorocarbons).
It is number 1 because enzymes are always being consumed.
A variation is a reference to the differences or deviations, such as the structure and form, as for crossing over is the exchange of genetic material between the non-sister chromatids of the homologous chromosomes during meiosis.
The Krebs cycle. The steps are
1. Glycolysis
2. Krebs Cycle
3. Electron transport chain.
The Calvin cycle is in photosynthesis.
