Topic: Half-Life
A certain element has a half-life of 1,000 years. How much of a sample of this element remains after 2,000 years?

Options:

25%

100%

50%

200%

4. discuss additional factors that some planets have that affect their seasons. 5. what fact about other planet’s seasons most surprised you and what did you find the most interesting? why?

How does pregnancy begin? a) a placenta forms in the uterus b) a sperm reaches an egg in the fallopian tubec) the blastocyst differentiates into two cell types d) contractions begin in the uterine wallapex

Drag each description to the correct location on the image. not all descriptions will be used. describe the parts of a comet. the frozen part of the comet the atmosphere of gases and dust formed when the nucleus vaporizes tail made of small, solid dust particles tail made of ions that appears to point away from the comet's orbit