In a dihybrid cross between individuals that are heterozygous for each trait, the four possible offspring phenotypes will be observed in the ratio of

3 : 1

Heterozygous trait is when for a particular gene or genes there are two different alleles.

Dihybrid cross between individuals that are heterozygous for each trait

Cross        A  x B

Genotype Hh x Hh

         H          h

H      HH       Hh

h       Hh        hh

Four possible phenotype : HH Hh Hh hh

Since 'H' is dominant allele and 'h' is recessive allele so dominant allele will express itself in both heterozygous and homozygous form.

3 : 1

the element that provides strength to the exoskeletons of clams and oysters is phosphorus.

this is so because calcium carbonate is the main component in the shells. calcium carbonate is strengthened by phosphorus.

explanation:

halogen, any of the six nonmetallic elements that constitute group 17 (group viia) of the periodic table. the halogen elements are fluorine (f), chlorine (cl), bromine (br), iodine (i), astatine (at), and tennessine (ts).