What Is the Main Reason for Warmer Summers in Middle

Multiple Choice

What is the main reason for warmer summers in middle latitudes?

A) The Earth is closer to the sun in summer.
B) The sun is higher in the sky, and we receive more direct solar radiation.
C) Ocean currents transport heat from the tropics to middle latitudes.
D) Plants in the mid-latitudes enhance the greenhouse effect.
E) Global warming causes this.