The excerpt is from an article that roberto read for science class called “using the scientific method to study tomatoes.” the student performed an experiment to test his hypothesis about sunlight and plant height using two plants. he kept everything the same between two tomato plants except he exposed them to different amounts of sunlight. he also used a third plant as a control group, or a group in which no variables are manipulated to confirm the results. roberto critiqued the work. which problem did roberto most likely identify? a. the sample size is too small. b.too many variables are manipulated. c.it is not possible to keep the conditions the same. d.controls should only be used in studies of animals.

The correct answer is that Roberto may have identified that the sample size is too small. Roberto is doing well with the scientific method in experimenting as using a control group and an experimental group that way formulating a good hypothesis for his experiment; such control can be used in other experiments, not just in animals or plants. It is possible to keep the conditions the same throughout the experiment but will need effort from the experimenter. Statistically speaking, his sample size is too small and it will affect his statistical analysis as with a small sample size, the margin of error is still to high and unpredictable.

The basic repeating unit of nucleic acids are known as nucleotides. a nucleotide consists of three distinct chemical groups.

answer: carbon 14 can only be used to determine the age of the organisms that were once living, and igneous rocks are non living.

explanation:

carbon 14 dating is used to determine the age of the sample by estimating the amount of carbon 14 present in the sample and then comparing it with a reference standard.carbon 14 is a isotope of carbon which is radioactive and unstable. carbon 14 is assimilated by all plants and animals throughout their life from carbon dioxide. however, one the organisms die they stop this assimilation and the carbon 14 content starts to decrease.by knowing how much of carbon 14 is left in an organism after his death, one can estimate the age of the organism. the materials whose age can be estimated by carbon 14 method are the organic compounds. however, some inorganic compounds such as aragonite   shell can also be dated.however, if we consider the igneous rocks it is a non living component which never accumulated carbon 14 in it and thus, we cannot use carbon 14 dating method to estimate its age.