what alternative energy sources could help our country depend on less foreign oil supplies, including, but not limited to, the environmental threats and any potential benefits to the United States and particularly for Texans.

Temperature and pressure

Ibelieve the answer is d. bleachhope my answer has you : )

Radon-222 or rn-222 has a half-life of 3.82 days. to determine the fraction of an original sample of rn-222 that remains unchanged after 7.646 days, we calculate the amount of rn-222 remaining after 7.646 days and divide it with the original amount. using 1 gram as a basis and using half-life calculation methods, we can determine that  0.249 or 0.25  grams of rn-222 will remain, and thus the fraction remaining is 0.25 or 1/4.