What the difference between similes and metaphor

Similes are a comparison of at least 2 things, but it compares them without using the word "like" or "as."  

Examples:

He walked as slow as a turtle.

The day was as hot as the sun.

Metaphors are the comparison of two or more things without using like or as.

Examples:

His face was a red tomato.

The road was a ribbon of moonlight.

b is the correct answer

conversing outside - a.