Answer:
The longest strand of DNA is the one that has descended the least in the electrophoresis gel. In other words, it is the one at the top of the gel.
Step-by-step explanation:
Electrophoresis is a process that separates DNA according to its size and charge. The scientist puts the DNA samples into the indents at the top of a special gel. Then the person places it in a box that contains an ionic solution, a positive electrode at the bottom, and a negative electrode at the top. As the DNA has a negative charge, it will descend through the gel's pores towards the positive electrode. Since there are DNA of different lengths, the shortest goes down quickly through the gel than the large strands. As a result, the short strands of DNA will be at the bottom of the gel, the medium size strands will be in the middle of the gel, and the large strands on the top of the gel.