Question

In mendel’s peas, plants homozygous for the recessive allele d are dwarfs. the dominant allele d determines the normal tall phenotype. to determine whether a given tall pea plant is homozygous or heterozygous for the d allele, you would cross the plant with

Answer 1

So, recessive allele 'd' are dwarfs. 
The dominant allele is 'D' determines tall. 
All you have to do is try to cross the alleles together to get either a homozygous or heterozygous remain. So, you should be able to get Dd or DD.