Answer:
Constant variables
Explanation:
Elaina's investigation lacked the critical ingredient of constant variables which are important components of every scientific investigation. In every research, there are 3 important variables, namely:
1. Dependent variables: the actual variable to be measured during the course of investigations and whose values are dependent on another variable (independent variable) supplied by the investigators.
2. Independent variable: one of the variables that are supplied by investigators whose values are often manipulated to see the kind of changes it will cause to the dependent variable.
3. Constant variables: other variables that are neither independent nor dependent but constant for all the various experimental groups in investigations.
The correct answer is the final option - sickle cell disease and malaria are both potentially lethal diseases.
The other options are incorrect because sickle cell disease is an inherited disease, but malaria is not - it is an infectious disease. However, both of these disease are quite dangerous, and may have severe consequences (such as death) if they are not properly treated.
Answer:
To burrow through the earth, a worm will flex its circular and longitudinal muscles to make itself long, then will extend the setae on its anterior, or front end to anchor itself in the earth. It will then contract its muscles to make its body short and bring the posterior, or back end, closer to the front.
Together with stratigraphic principles, radiometric dating methods are used in geochronology to establish the geologic time scale. Among the best-known techniques are radiocarbon dating, potassium–argon dating and uranium–lead dating.
