Ascientist wants to use a model to present the results of his detailed scientific investigation.
why would a model be useful?
o because the model makes the concepts easier to understand
because the model is easy to put together and to use
because the model prevents other scientists from asking questions
because the model requires the audience to pay full attention to it

The correct answer is A. Because the model makes the concepts easier to understand

Explanation:

A model refers to a three-dimensional representation of an object or idea. This means in the case of a model to represent the results of a scientific investigation, this is a way to represent visually what scientists found during a research process. In this context, using models has some benefits because due to models being visual these are easier to understand than texts, especially if people are not experts in the topic or the results include complex concepts as models represent visually complex ideas. Thus, a model would be useful "because the model makes the concepts easier to understand".

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

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