1. it is difficult to search for it . Because infrared rays will never penetrate through earth atmosphere.
2. we are unaware of how it looks like and we only know it is red and will glow . A damaged star also looks like this.
3. Dust also makes is hard to detect Dyson spheres . So we will get confused between Dyson sphere and a star surrounded by dust.
Electric field due to a point charge is given as

here we know that

also the distance is given as

now we will have

so we will have

so above is the electric field due to proton
Answer:
Friction, normal force, and weight
Explanation:
If the book slows down, it means that there must be friction acting in the opposite direction of the direction the book is moving in.
Weight is caused by the gravitational pull of the Earth on the book, and normal force is the table pushing the book up because the book is pushing down on the table (3rd law.)
Note that weight and normal force is not the 3rd law action-reaction pair. The pair is the force of the book on the table and the force of the table on the book.
%d is a format specifier that is a placeholder for an int value. It tells the compiler that we want to print an integer value that is present in variable a. In this way there are several format specifiers in c.
Your answer is C) The year the element was discovered :)