This core has stayed hot over the billions of years since. Every kilometer you go down, it gets about 25 degrees Celsius hotter (or 1 degree Fahrenheit per 70 feet). The core will never freez over. Scientists estimate it would take about 91 billion years for the core to completely solidify. The sun will burn out long before that time!

Which two words would BEST replace estimate" and "solidity in the paragraph above?
(A) guess; freeze
(B) hope; set
(C) predict: harden
(D) assume, congeal

Sampling lake water for microscopic organisms is not as easy as it sounds when you want to both count and identify species. in a given water sample, your bacteria of choice can be rare or difficult to culture, particularly given the mixture of bacteria in a biofilm. which of the following culture media would be best for growing fecal coliforms when they are relatively less abundant than other bacteria in the lake? anaerobic culture medium enrichment culture medium complex culture medium basic culture medium

Which codon is the code for the amino acid histidine (his)?

In what for do plants utilize nitrogen? why do they need nitrogen?