On stages 13 (28 days) and 20 (50 days), and compare limb development at these stages. and thee answer for this isin stage 13, all four limb buds are present. in stage 20, the upper limbs are slightly bent at the elbow. in stage 20, the fetus has short, stubby fingers. in stage 20, the hands curve over the cardiac region.

Ans.

Limb development can be defined as formation of limbs in embryo as the result of interactions between ectodermal and mesodermal components of the limb buds. In humans, it is divided into 23 stages. Stage 13 and stage 30 can be compared as given below:

Stage 13 represents the first stage, at which all four limb buds are present, During this stage lens disc appears for the first time and closure of otic vesicle takes place.

Stage 20 represents limbs with greatest length, upper limbs are slightly bent near elbow. At this stage, fetus has small and stubby fingers, with slightly curved hands.

an organism's phenotype is the  form of a trait  that it  displays. for  flowercolor, a pea  plant  can  display  a phenotype of purple or white flowers. an organism's  genotype  is the alleles of a gene it contains. based on his data, mendel concluded that a phenotype can be  determined  by more than one  genotype.

endo:

regulates body hormones, aldosterone, vasopressin

neural:

signal, regulates body using electric signals, reflex

endo has to do with hormones; aldosterone and vasopressin are both hormones. i also had this question and got it right : d