Which of the following are NOT possible candidates for dark matter?Group of answer choicesBlack holesBrown DwarfsMACHO'sRed Giant Stars

Red Giant Stars are not possible candidates for dark matter.

Here's why:

1. Black Holes: They are considered as a possible candidate for dark matter because they do not emit or reflect light and have strong gravitational effects, which are the main characteristics we associate with dark matter.

2. Brown Dwarfs: These are also considered as a possible candidate for dark matter. They are objects which are too large to be called planets and too small to be stars. They have insufficient mass to sustain nuclear fusion, so they do not emit substantial light or heat.

3. MACHOs (Massive Astrophysical Compact Halo Objects): These are another possible candidate for dark matter. They are large, dense objects such as black holes or brown dwarfs that reside in the halos of galaxies.

4. Red Giant Stars: These are not considered a candidate for dark matter. Red giants are a phase in the life cycle of a star and they emit light and heat, which contradicts the characteristics of dark matter. Dark matter is believed to be non-luminous, meaning it does not emit or interact with electromagnetic radiation, and is therefore difficult to detect.