Answer:
The correct answer will be option-pollen.
Explanation:
The pollen are the male gametophyte which is produced in the seed plants.
The pollen produce male gametes after entering the female gametophyte. The male gametes fuse with the egg cell and form the embryo inside ovary which matures and forms seeds.  The vascular seed plants lack these pollen but instead produces male gametes in gametangia which are replaced by the pollen in the seed plants.
Thus, option-pollen is the correct answer.
 
        
             
        
        
        
Answer:
B. Hardness
Explanation:
Physical properties of a substance is defined as the properties which can be observed or measured without changing the composition of matter. 
Physical properties include odor, appearance, color, texture, boiling point, melting point and many others.
Hardness is a physical property of a substance as it describes the  resistance of substance to deformation and can be observed by simple touch or without changing the composition of matter.
While reactivity, toxicity and flammability are chemical properties of substances that change one type of matter into another type.
Hence, the correct option is B.
 
        
             
        
        
        
Answer:
D. Each enzyme can catalyze a wide variety of different reactions
Explanation:
Each enzyme can only catalyze a few, specific types of reactions.
Since enzymes and substrates are very specific to one another, enzymes cannot catalyze a wide variety of reactions. 
If a substrate is not the correct one that fits in the enzyme's active site, a reaction will not occur.
So, each enzyme can only assist in a few reactions.
The correct answer is D. Each enzyme can catalyze a wide variety of different reactions
 
        
             
        
        
        
Answer:
(A). Sexual reproduction increases genetic diversity, and asexual reproduction can be more rapid.
Explanation:
Sexual reproduction is a mode of reproduction, which involves formation of new organisms by combination of genetic information from two organisms of different sexes. The major advantage of sexual reproduction is to develop genetic diversity as new organism is produced by mixing up genetic material of both the parents.
On the other hand, asexual reproduction involves formation of new organisms from a single parent having identical genetic makeup as present in parent cell.  One of the major advantage of asexual reproduction is to produce high number of offspring in less time as it is more rapid than sexual reproduction. 
Thus, the correct answer is option (A).