Stating that an organism is heterozygous is staying its a. b. . test cross

Option A, Genotype

Explanation:

Genotype is the representation of allele pair acquired by an offspring after a cross is carried out between its parents (who too have a certain genotype)

When the two alleles of any particular trait in any individual are exactly similar to each other then the genotype of the individual is said to be homozygous while when these two alleles different from each other then the genotype of the individual is said to be heterozygous.

For example - if "T" and "t" are two alleles for height of an individual, then "TT"  and "tt" represents the homozygous genotype while the "Tt"  represents the heterozygous genotype

Hence, option A is correct

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.