Why is it important to have control in a lab

Aseries of connections of food chain in an ecosystem is called a what

Aflame cell is at the end of each tubule of the nephridium malpighian tubules kidneys none of the above

What do isotopes of uranium have the same number of? what do they have a different number of? a) same number of protons; different number of electrons b) same number of protons; different number of neutrons c) same number of electrons; different number of protons d) same number of neutrons; different number of protons