Here's a problem to solve: Two identical plants are planted 3 meters apart. One plant is flowering, but the other is not. A student concludes that the plants are receiving an unequal supply of water. Another possible explanation the other plant is not flowering is that the plants are

Among the 4 following options, which is the correct answer?

- A: too close to one another.
 
- B: receiving different amounts of sunlight.
 
- C: in soil with high humus content.
 
- D: receiving different amounts of carbon dioxide.
 