Flower color in Hydrangea macrophylla plants is thought to be determined primarily by soil conditions rather than by inherited differences. Which of the following will provide the most direct evidence that flower color in Hydrangea macrophylla is due primarily to soil conditions?
a. comparing DNA sequence information for Hydrangea macrophylla to DNA sequence information for a different species of flowering plant
b. performing a genetic cross between a pink-flowered plant and a blue-flowered plant and then determining the ratio of phenotypes in the offspring
c. growing cuttings from the same Hydrangea macrophylla plant under controlled conditions that vary only with regard to soil pH
d. analyzing fossilized remains of an ancestral species that grew in geographic areas similar to the habitats of modern Hydrangea macrophylla.

The answer is C.

Explanation:

The Hydrangea Macrophylla plants' flower color which are either blue or pink, is thought to be determined according to the soil's conditions that the plant is planted in. The most effective method that will prove this statement is if two branches of the Hydrangea Macrophylla plant is taken and put into two different soils which have controlled pH levels, and then the plants can be observed for any differences that will certainly be caused by the soil.

I hope this answer helps.

The correct answer is option c. "growing cuttings from the same Hydrangea macrophylla plant under controlled conditions that vary only with regard to soil pH".

Explanation:

A experiment that would prove that flower color in Hydrangea macrophylla plants is determined primarily by soil conditions is growing cuttings from the same Hydrangea macrophylla plant under controlled conditions that vary only with regard to soil pH. If the cuttings of the same plant (which means that they have the same genotype) develop different flower colors, it will prove that this trait is determined mainly by the soil pH.