The first words out of my mouth were "official or unofficial?"
a. Mankato, Minnesota
b. Santee "Sioux" Indians
c. 38
d. I was going to say "for being alive" but it's more like "for being in the way of the white settlers after they took over the Dakota's land, took their food supply, broke every treaty they had signed, created famine, then refused to relieve it." For the resulting war, 303 Indians were convicted in a five-minute trial and sentenced to death. Only 38 were hung, but the rest were banished from their homes (which the white settlers thought very convenient) to a drought-stricken area in the Dakotas where many starved to death, so technically it *was* a death sentence, but that's unofficial.
Edit - Part a of the question asked when, not where, the execution took place, so Mankato, MN is not a correct answer.
Part d of the question was asking for the official crime of which those executed were accused, so though your indignation is fully justified, your answer can't be accepted.
As I said recently in grading another question, the people who compose the questions do their best to avoid ambiguity, but it cannot always be anticipated how players will interpret a question.
Hoosier