How many aminoacyl-trna synthetase enzymes must be present in cells to properly synthesize proteins?

a., 3, one for each base in a codon
b., 4, one for each base in the mrna
c., 20, one for each amino acid
d., 64, one for each possible codon

In 2015, about ten percent of total u.s. energy consumption was from renewable energy sources. renewable energy plays an important role in reducing greenhouse gas emissions. when renewable energy sources are used, the demand for fossil fuels is reduced. sanjay and his family want to cut back on their use of non-renewable resources at home. they are thinking of an alternate way to heat their home without adding more greenhouse gases or pollutants to the environment. which renewable resource would not fit into their plan? a) solar power b) burning wood c) constructing a wind turbine eliminate d) generating hydroelectric power

Which of these is an example of land degradation? a. containers designed to store pollutants leak. b. fertilizers provide too many nutrients to crops. c. garbage is buried so the land can be reclaimed later. d. a drought kills all the plants in an area, leaving bare land

Which of the following is the sl unit used to measure temperature a. kilogram b. liter c. meter d. kelvin