9:3: 3:1  is the phenotypic ratio showing traits as black and long hair : black and short hair: chestnut and long hair: chestnut and short hair when a chestnut horse heterozygous for pacing and hair length with a hybrid horse. 
Explanation:
Dominant trait = black hair colour (BB,Bb), trotting (TT,Tt) , long hair (LL,Ll)
recessive trait = chesnut hair colour (bb), pacing gait (tt), short hair(ll)
cross between chestnut horse heterozygous for pacing and hair length will have alleles as BbLl 
alleles for hybrid horse will also be heterozygous Bb, Ll
Punnett square to show the cross:
       BL         Bl       bL         bl
BL  BBLL  BBLl     BbLL    BbLl
Bl   BBLl    BBll     BbLl      Bbll
bL  BbLL  BbLl      bbLL     bbLl
bl    BbLl  Bbll       bblL        bbll
phenotype ratio 
black and long hair : black and short hair: chestnut and long hair: chestnut and short hair
9:3: 3:1  is the phenotype ratio.
 
        
             
        
        
        
The stem of the plant should be cut at least three to four centimeters above the surface level.
The stem should be tightly fixed into the glass capillary.
All connection should be made air-tight by using paraffin.
Initial and final readings should be carefully noted.
        
             
        
        
        
Answer:
the answer is b.The model should show the original stem cell dividing to become a differentiated cell and another stem cell.
Explanation:
 
        
             
        
        
        
Answer:
b. pseudocoelom
Explanation:
A pseudocoelom is a false body cavity of some invertebrates which occupies the space localized between the mesoderm and the endoderm of the gut. This false cavity is found in nematodes.
Arthropods exhibit:
1- Bilateral symmetry because both opposite sides of the body are similar,
2- they are protostomes because the blastopore becomes the mouth during embryonic development,
3- they have true tissues because tissues are formed by groups of cells which share a common function, and finally,
4-arthropods are triploblastic because they are formed by three germ embryonic layers (endoderm, mesoderm and ectoderm).