题干

下列说法中不正确的是(   )

A:如何提高燃烧效率,节约能源是当今世界各国能源研究的前沿课题之一

B:物质燃烧一定是放热反应

C:绿色植物进行光合作用时太阳能转化为化学能

D:增加炼铁高炉的高度,可以降低高炉气中CO的含量

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D

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    Here are Important Travel Notices from United Airlines, March 20, 2016 7:12 AM. Information is updated as it is received.

    ⒈Travel and the Zika virus

    If you have a ticket for travel to a country affected by the Zika virus(as listed on the CDC website) and have concerns, please contact the United Customer Contact Center with any questions or changes to your reservation. Customers advised to avoid the affected regions based on CDC guidance may change their destination or travel date without a fee or may choose to receive a refund(退款) if their tickets were booked before February 29,2016. The new travel date must be within the validity of the ticket. Additional charges may apply if there is a difference in fare for the new travel route.

    ⒉Longer lines at security checkpoints

    Procedural changes at TSA checkpoints throughout the United States may result in longer lines at security checkpoints. Please plan accordingly and allow for extra time at the airport. The TSA advises arriving at the airport two hours before your flight for US travel and three hours before for international travel. To save time at security, we encourage you to visit www.tsa.gov.com and apply for TSA pre-check.

    ⒊Notice for flight departing the European Union, Norway and Switzerland

EU Regulation 261/2004 requires airlines to provide the following notice: If you are not allowed to board or if your flight is canceled or delayed for at least two hours, ask at the check-in counter or boarding gate for the form, stating your rights, particularly about compensation assistance.