(01.01 mc) carlos is trying to determine how music affects the growth of bean plants. he hypothesizes that classical music will cause a plant to grow at a higher rate than no music or rap music. he grows nine bean plants in similar lighting, temperature, and soil conditions. three are exposed to classical music 24 hours a day, three are exposed to rap music 24 hours a day, and three are grown in complete silence. carlos measures the growth of the plants every day and finds that the plants all seem to have the same rate of growth. what is missing from carlos's scientific investigation? a specific hypothesis predicting a relationship between independent and dependent variables controlled variables to ensure only the independent variable is being changed experimental data collected regularly that can be recorded and analyzed research on what other scientists have observed and investigated on this topic

The purpose of the experiment conducted by Carlos is to study the affect of music on the growth of bean plants. He hypothesized that the rate of plant growth will be higher in the presence of classic music than rap music or without music. All the bean plants were exposed to similar environmental conditions like light, temperature and soil conditions. The independent variable was exposure to music (classic, rap or no music). The dependent variable is plant growth and control variables are  light, temperature and soil conditions. His scientific study lacked a research or background information on what other scientists have experimented on the same topic.

So, the correct answer is Research on what other scientists have observed and investigated on this topic.

Research on what other scientists have observed and investigated on this topic

Explanation:

Carlos included a :

Hypothesis: classical music will cause a plant to grow at a higher rate than no music or rap music.

Controlled variable: three are grown in complete silence.

Experiment data: Carlos measures the growth of the plants every day and finds that the plants all seem to have the same rate of growth.

but the only thing he is missing is research from other scientist.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.