Premise:
"It was the main entrance to the castle, and a formidable obstacle to the enemy."
Hypothesis: It was the primary way to enter to castle and a big roadblock for the enemy.

yes

Premise:
"The Commission also assumed that the average revenue per piece for the 21 industrial countries whose rates were available applied to the remaining 5 ICs whose rates were not available."
Hypothesis: The commission assumed the countries with rates that were unavailable were similar to the other countries.

yes

Premise:
"They made Parameswara an offer he could not port facilities and an annual financial tribute in exchange for Chinese protection against the marauding Thais."
Hypothesis: The Chinese refused to negotiate, and instead gave the Thais free rein to continue their attacks.
no