Frictional force and Applied force has same “magnitude” and “opposite” direction.
Option: B
<u>Explanation</u>:
When a book is moved horizontally by applying “force” on the book, the frictional force is opposed to the book by the table. Here, this “frictional force” is opposing the book has the same force what we applied on the book but this frictional force and the applied force are opposite in direction. Always the “frictional force” is opposite to the “applied force” which stops the object to move. For example, if a force applied leftward to the object the frictional force is acted on the right side of the object.
When two objects are in contact they experience a "frictional force". This "frictional force" acts opposite to the force applied on to move the object.
Formula for "frictional force" is 
Where,
is coefficient of friction and N is normal force.
If you drop a 50 gram piece of metal that has a temperature of 110°Celsius into 1000 grams of water at 25°Celsius, <span>D.)The water and the metal’s temperature will reach the same temperature. In any system undergoing heat transfer, the objects involved will eventually reach the same temperature, signifying thermal equilibrium.</span>
D is the answer
Velocity maybe negative or positive
while speed is always positive