Many cities have “combined” sewers. in good weather, these systems funnel sewage to treatment plants. during rainstorms street runoff is combined with sewage. combined sewers in cities can be problematic because the sewers cannot handle the volume of waste from street runoff and sewage sewers are often blocked by trash that people have thrown into them street runoff cannot flow into the sewers and be safely taken to treatment plants street runoff often causes the sewers to deteriorate

The given blank can be filled with the sewers cannot handle the volume of waste from street runoff and sewage.

The combined sewage system is very popular in many big cities. The sewage system handles all the sewage combining from the houses. During the rainy season, the water flows in the sewer, causing the overflow of the sewers and spread of water in the nearby regions.

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.'