How is carbon dioxide obtained?

Asample of radium-226 will decay 1/4 of its original amount after 3200years. what is the half-life of radium-226?

Sex cells from female reproductive organ? 1) mitosis 2) fertilization 3) zygote 4) eggs 5) meiosis 6) sperm

In which environment would primary succession occur? a forest with a few remaining trees after a recent wildfire an area of exposed rock after a glacier melts away beach that is exposed to the air at low tide an abandoned baseball field in a small town