Which statement about cell division is true?
a. a cell divides once during meiosis and twice during mitosis.
b. a cell divides once during mitosis and twice during meiosis.
c. a cell divides once during mitosis, but it does not divide during meiosis.
d. a cell divides once during meiosis, but it does not divide during mitosis.

Certain bacteria (such as aquaspirillum magnetotacticum) tend to swim toward the earth’s geographic north pole because they contain tiny particles, called magnetosomes, that are sensitive to a magnetic field. if a transmission line carrying 100 a is laid underwater, at what range of distances would the magnetic field from this line be great enough to interfere with the migration of these bacteria? (assume that a field less than 5% of the earth’s field would have little effect on the bacteria. take the earth’s field to be 5.0 * 10-5 t, and ignore the effects of the seawater.)