Answer: If a husband and wife who are both carriers of the sickle-cell anemia allele (Ss) but do not have the disease decide to have a child, the offspring can be Normal (SS), carrier (Ss) or sick (ss) with the probability ¼, 2/4 (½) and ¼ respectively. 
Explanation: If the mother contributes the dominant allele and the father also contributes the dominant allele, the genotype of the child will be SS. The probability is ¼. This means there is a 25% chance that a randomly selected offspring will be a normal child and will not have sickle-cell anemia.
If the mother contributes the dominant allele and the father contributes the recessive allele, the genotype of the child will be Ss. The probability is 2/4 or ½. This means there is a 50% chance that a randomly selected offspring will be a carrier of sickle cell anemia, but will not have sickle-cell anemia.
If the mother contributes the recessive allele and the father also contributes the recessive allele, the genotype of the child will be ss. The probability is ¼. This means there is a 25% chance that a randomly selected offspring will have sickle cell anemia. 
Check attached image for illustrations. 
 
        
             
        
        
        
Answer:
Such five changes or steps occurring during seed germination are: (1) Imbibition (2) Respiration (3) Effect of Light on Seed Germination(4) Mobilization of Reserves during Seed Germination and Role of Growth Regulators and (5) Development of Embryo Axis into Seedling.
 
        
             
        
        
        
Acid rain, or acid deposition, is a broad term that includes any form of precipitation that contains acidic components, such as sulfuric acid or nitric acid. The precipitation
        
                    
             
        
        
        
Answer:
They can be found in several trophic levels, as they are related with several trophic level, hence, they cannot be placed on a specific trophic level.
Explanation:
A trophic level is a specific position occupied by a group of organisms on a good chain in relation to their nutrition.
Dentrivores feed on the waste of other organisms and cannot be really placed on a specific trophic level, likewise decomposers, of which they feed and decompose the body of organisms.
Omnivores feed on both plants and animals, which includes producers and consumers. Placing omnivores on a specific trophic level would not be really straightforward also.
 
        
             
        
        
        
Answer:
The correct answer will be-
1. Arthropods are named for their jointed appendages.
2. Both nematodes and arthropods possess an external covering, or cuticle.
3.  Some nematodes are parasitic on humans.
4.  Arthropods possess an open circulatory system.
5.  Both nematodes and arthropods must molt in order to increase in size.
Explanation:
Ecdysozoa is the largest group of animals which includes the largest phylum called the Arthropods and the nematodes along with other small phyla.
The members of this superphylum are characterized by having an outer covering called "cuticle" which protects the animal from the water loss and external environment.
The members moult while they grow in size and shed their cuticle and forms a new cuticle layer after moulting.
Nematodes are pseudocoleomates which are parasitic in nature and can cause elephantiasis which involves swelling of the lower part of the humans.
An arthropod is a group of small organisms which is marked by the jointed legs. Their circulatory system is open circularity system as they lack blood vessels to transport fluid.
Thus, the selected options are correct.