Occur when two meet.
a) air masses, fronts
b) fronts, air masses
c) cyclones, fronts
d) fronts, clouds

B) Fronts, air masses

When the air masses meet fronts are formed. These fronts reflects the weather condition of a region.  

Cold front forms when a cold air mass slides under a warm air mass, resulting in the warm air mass to rise above. This is responsible for cold weather conditions.  

Warm front forms when a moist warm air mass slides over the cold air mass. This is responsible for gentle rain and snow.

Stationary front is forms when warm and cold air neither meet nor able to displace each other. These air masses remain in the stationary condition. This is responsible for cloud formation and precipitation.  

Occluded front is formed when a warm air mass gets caught between two cold air masses. This is responsible for strong wind and heavy precipitation.  

economic impact of malaria is estimated to cost africa $12 billion every year. this figure factors in costs of health care, absenteeism, days lost in education, decreased productivity due to brain damage from cerebral malaria, and loss of investment and tourism.

ans.

dna fingerprinting is defined as a process that determines the dna characteristics of an individual. these dna characteristics are unique among individuals as their fingerprints, so it is known as dna fingerprinting.

steps of dna fingerprinting includes extraction of dna from sample, amplification of dna, restriction digestion of amplified dna, and then analysis of dna by gel electrophoresis, respectively.

thus, the next step performed by the scientist is 'to cut the amplified dna (obtained by polymerase chain reaction) by restriction enzymes that cleave the dna into fragments and their analysis.'