The number 4 in the 4/2He indicates the atomic mass number of helium.
Answer: Option 3
<u>Explanation:
</u>
The elements present in periodic table generally represented as 
. Here X will be the element in the periodic table, A is the atomic mass number of the element X and Z is the atomic number of the element X.
So, the number 4 is the atomic mass number of He and He-4 is the stable isotope of helium which can also be termed as alpha particle.
Mass number = number of protons + neutrons count.
Thus the number 4 denotes the Helium's atomic mass number.
Answer: A bike
A bike is composed of various simple machines. It has a wheel and axle as one component, and it also has screws to hold the various parts together, along with levers and pulleys that are connected to the pedals. So all of these simple machine concepts work together to help transport the rider from point A to point B.
The other answer choices of screw, inclined plane, and lever, are fairly simple machines that don't have many things going on at once compared to a bike.
Isotopes have same atomic number but different atomic mass number.
Hence option B is correct.
Hope this helps you!
The radiation emitted is a beta particle with a -1 charge. Beta particles have a <span>medium penetrating power. An emission of beta particles requires shielding because of the hazards it pose to humans. Thus, one characteristic of this radiation is that <span>some shielding is required.</span></span>
