Alpha particles are positively charged and contain the nucleus of ……….atom.
A.$He$
B.$H$
C.$Li$
D.${H^ + }$

Hint:An alpha particle is a fast-moving packet produced during the alpha decay. An alpha particle can travel only a few inches through air. They can be stopped with the help of a sheet of paper.

Complete step by step answer:
Alpha particle is also known as alpha rays or alpha radiation. Alpha particle is a positively charged particle. It contains two protons and two neutrons. i.e. the charge on the alpha particle is a two-unit positive charge and mass is four-unit. Hence it contains the nucleus of the helium atom.
Hence the correct answer is option A.

Additional information: Alpha particles are named after the first letter in the Greek alphabet,α. Since they resemble helium atoms sometimes they are represented as $H{e^{2 + }}$. Alpha particles are a highly ionizable form of particle radiation and have low penetrating depth. They are commonly emitted by all of the larger radioactive nuclei such as uranium, thorium, actinium, and radium as well as the transuranic elements. Sometimes, extremely high energy helium nuclei referred to as alpha particles make up about 10-12% of cosmic rays.


Note:
There are many ways in which alpha particles are used:
Alpha particles are used in the treatment of various types of cancer.
It is also used in a smoke detector. In this alpha particle from americium-241 is used.
Alpha particles are also used as an energy source to power heart pacemakers.
Alpha particles are used to provide a heating effect in spacecraft.
In oil industries, the alpha particles are used to power some of their offshore equipment.