It is to be noted that the note indicated in the image will get one and a half beats. (Option C) See the attached.
The beat is the fundamental time unit, or pulse, of the mensural level in music and music theory.
Though this definition may not be accurate in real life, the beat is commonly understood to be the rhythm that a listener would tap their toes to while enjoying a piece of music or the numbers a musician counts while playing.
It is important to remember that the beat serves as a prompt for all of the musicians to play their instruments in perfect time with the song and one another.
It's what combines the musical parts to create a coherent and well-fitting tune.