Which of the following shows the greatest promise as a cancer chemotherapy agent?

a) a drug that interferes with organismal cellular respiration
b) a drug that prevents tetrad formation
c) a drug that prevents crossing over
d) a drug that prevents mitotic spindle from forming

d) a drug that prevents mitotic spindle from forming

Explanation:

for many years now, the mitotic spindle fibers are the promising target for anticancer drugs.  The mitotic spindle are fibers which during mitosis are responsible for separation of chromosomes between the two daughter cells.  The anticancer drugs specifically arrest the spindle  fibers segregation point and halt the mitosis of cells for long period of time which will stop cancer cell division.

D) A drug that prevents mitotic spindle from forming.

Explanation:

Drugs that prevent mitotic spindle formation for example Taxol (Paclitaxel) have been used very effectively in chemotherapy because they poison microtubles and inhibit the mitotic spindle. This in turn stops cancer cells from dividing and causes them to die.

The ansseer is Iridium.

The atomic number of iridium is 77 and it comes just before platinum (atomic number = 78).

In iridium,

The number of electrons = no. Of protons = 77.
The no. Of electrons and the no. Of protons is same as atomic number.