Answer:
number 1: heat from the sun or solar energy
Nucleus, electrons are found in shells or orbitals that surround the nucleus of an atom, protons and neutrons are found in the nucleus. They group together in the center of an atom.
Selectively permeable (or semi permeable) means where for example a membrane can choose what material can pass through while others cannot. They control the in and out of materials.
This is because the membrane has tiny spaces, where only smaller molecules can pass through, other larger ones cannot.
<span>Homologous chromosomes exchange DNA during meiosis in a process called crossing-over. Crossing-over sometimes involves an unequal swapping of DNA. Basically one chromosome in the pair gets extra DNA.</span>
I would say to be safe age 11.
