D. <span>controlled
is the right answer because a</span><span>n </span>experiment<span> in which an observer tests a hypothesis by looking for changes carried by alterations to a variable.</span>
Mutations. Definition. A Mutationoccurs when a DNA gene is damaged or changed in such a way as to alter the genetic message carried by that gene. A Mutagen is an agent of substance that can bring about a permanent alteration to the physical composition of a DNA gene such that the genetic message is changed
Hypothesis is a proposed explanation which is made on the basis of given experimental data taken as starting point for further investigation. All hypothesis test are conducted in a same manner fiollowing the four main steps:
1. State the hypothesis
2. Formulate an analysis plan
3. Analyzing the data obtained
4. Final step is to analyze the results
There are three types of variables taken in an experiment:
1. Independent variable: light, temperature, humidity
2. Dependent Variable: these depends upon the other variable. changes in the independent variable may cause the dependent variable to change, for example, growth of plant is a dependent variable which depends upon the amount of light(independent variable), the plant receives
3. Controlled Variable: these variable can be controlled and prevented from being change like ty[pe of plant, type of soil
Answer:
Masks are a simple barrier to help prevent your respiratory droplets from reaching others. Studies show that masks reduce the spray of droplets when worn over the nose and mouth.
Explanation: