单语范例（未经PONS编辑处理）
It is doubtful the mangrove forests can sustain this level of harvesting.
en.wikipedia.org Early designs allowed for the pilot to escape after the final acceleration towards the target, although whether this could have been done successfully is doubtful.
en.wikipedia.org This opinion was pronounced neutral; a second inquiry was called for, and this time the qualifications of the expert for the task were doubtful.
en.wikipedia.org Therefore, in no doubtful case will the judiciary pronounce a legislative act to be contrary to the constitution.
en.wikipedia.org Without the existence of statistical estimates of chance collisions, conclusions based on comparison alone are thus viewed as doubtful.
en.wikipedia.org