A small zone of fluorescent microtubules in a cell is photobleached so that their fluorescent label gives off no light. Some time later fluorescence returns to the bleached zone in the cell. Which of the following is a possible explanation for the recovery of fluorescence in the region of the cell previously bleached?a) the dynamics of the microtubules turning over in that bleached zone of the cellb) the growth of new microtubules into the bleached zonec) movement of microtubules through the bleached zoned) all of these choicese) the dynamics of the microtubules turning over in that bleached zone of the cell and the growth of new microtubules into the bleached zone