Scientists are testing substance L to determine how it enters mammalian cells in a culture. The cells maintain a 120 millimolar (mM) intracellular concentration of substance L. The scientists determined the rate of entry of substance L into the cells at various external concentrations of substance L (10 to 100 mM) in culture medium (Table 1). Table 1. Rate of entry of substance L into mammalian cells in culture
External concentration of substance L (mM) Rate of entry of substance L into cell as a percent of maximum
10 5%
20 25%
30 45%
40 65%
50 80%
60 90%
70 95%
80 100%
90 100%
100 100%
The cells maintain substance L at an internal concentration of 120 mM.
Determine the external concentration of substance L that will result in one-half of the maximal entry rate.

Which statements best describe the differences or similarities between a comparative investigation and an experimental investigation? check all that apply. experimental investigations are best for showing cause-and-effect relationships, while comparative investigations do not necessarily show this type of relationship. comparative investigations are often impractical and unrealistic, while experimental investigations are the most practical and realistic kinds of investigations. comparative investigations allow for the use of a wide range of variables but do not have a control group, while experimental investigations involve variables that can be controlled. both experimental investigations and comparative investigations are designed to answer scientific questions. both experimental investigations and comparative investigations focus on making observations rather than collecting new data.