Which courts have original jurisdiction over nearly all civil and criminal cases heard in federal courts?
a. admiralty courts
b. district courts
c. circuit courts
d. state courts

The correct answer is B. District Courts.

B. District Courts have original jurisdiction over nearly all civil and criminal cases heard in federal courts, since these are courts that, together with the Courts of Appeal and the Supreme Court of the US, conform the Federal Judicial System. They have been set up in each of the fifty states and the District of Columbia. There are ninety-three in all.

Moreover, the other answers are incorrect because:

A. Admiralty courts hear cases of maritime issues.

C. Circuit Courts and D. State Courts have jurisdiction only over state matters, since they depend on the State Judicial System.

explanation:

a trial judge has broad powers in his courtroom. the judge's decision is usually final for the duration of the trial, and the party's one special type of witness is an expert witness.