最近，中共中央发布改进工作作风的八项规定，大力提倡“例行勤俭节约、严守廉洁从政”。古时候即有“居安思危，戒奢以俭”的皇帝，他在魏征劝谏后，即能身体力行、持之以恒，这位皇帝是（    ）

已知集合A={0,1,a}，B={2,a²}，若$A\cup B=\left\{0,1,2,3,9\right\}$,则a的值为（    　）

    New Sciencenter Featured Exhibition: Ocean Bound!

    Opening weekend

    Member Preview: Friday, February 3, 6—8 pm

    Public Opening: Saturday, February 4, 10 am — 5 pm

    Start a journey through watersheds to see how everyone's actions affect the health of our ocean. Enjoy interacting with 3D watershed models, piloting a full-size submersible from mountain stream to ocean, guiding water safely through a hazardous maze, diverting pollutants as they travel through storm-water drains, playing with early education exhibits inside a clubhouse, and many more engaging interactive exhibits.

    Showtime! Plant and Animal Double-Takes

    Saturday, January 21, 2 pm

    Have you ever looked at a living thing and wondered, Is that a plant or an animal? Join Sciencenter educators Julie Yurek and Sarah Cox to look into species that make you take a second look. Explore the surprising differences between these plants and animals.

    Showtime! Solar Power Goes Nano

    Saturday, February 11, 2 pm

    Did you know scientists are using nanotechnology to store solar energy? Learn about solar power and the emerging use of hydrogen fuel cells. Justin Sambur, NSF Postdoctoral Research Associate at Cornell's Department of Chemistry and Chemical Biology, will demonstrate a model race car that uses a hydrogen fuel cell kit powered by solar energy.

    Special Showtime! Presentation: Animal Adaptations for Winter

    Wednesday, February 22, 1 pm

    Have you ever wondered how animals survive in winter? Join Emma Brofsky of Cornell's Naturalist Outreach Program to explore animal adaptations for winter and learn how biology helps animals cope with cold weather, food shortages, and limited habitats. Touch animal pelts and do a hands-on activity on animal insulation.