Under the allotment system, many american indian families
a. did not try to farm and ignored the government policy
b. were successful farmers and competed with white settlers
c. tried to farm communally and established their own system
d. made an effort to succeed at farming but often failed

I believe the answer is: D. made an effort to succeed at farming but often failed.

Under allotment system, Indian families were provided with a communal garden that they can use for their consumption only (non-commercial purpose). At that time, the given land was too small to fulfil the consumption needs of the Indian families, which made this system eventually failed.

d. japan's attack on pearl harbor

a.impressment of us soldiers