题干

水稻(基因型为AaBb)的花药通过无菌操作,接入试管,经过右图所示的过程培育试管苗。以下选项中正确的是(  )

A:a用花药离体培养法获得单倍体植株;b通过有丝分裂产生愈伤组织;c培养基中至少应有乙烯和脱落酸;d试管苗的生长发育不需要光照

B:a用花药离体培养法获得二倍体植株; b通过减数分裂产生愈伤组织;c培养基中至少应有生长素和细胞分裂素;d试管苗的生长发育不需光照

C:a用花药离体培养法获得单倍体植株;b通过有丝分裂产生愈伤组织;c培养基中至少应有生长素和细胞分裂素;d试管苗的生长发育需要光照

D:a用花药离体培养法获得二倍体植株;b通过有丝分裂产生愈伤组织;c培养基中至少应有乙烯和脱落酸;d试管苗的生长发育需要光照

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C

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    Currently offered by some famous universities, MOOCs are attractive to people who do not have the financial resources to meet the growing costs of university education, or who do not have formal qualifications. They also allow participants to study at their own pace.

    The potential for MOOCs to deliver education is obviously vast—they could be considered as a huge step forwards in widening participation. They also have the potential to provide a unique window on universities that offer popular and valuable courses, they may attract some participants to register for formal fee-paying programmes at the same or other universities and are likely to promote new ways of on-line education.

    However, it is still very early days for MOOCs. The quality of the education provision is highly variable, with many courses offering only recordings of lectures, and delivery is particularly difficult in some special fields that require practical classes, research projects or extensive library access. Besides, wider engagement with participants requires very considerable resource. Even limited feedback or examination becomes a major task if there are several thousand students in the class.

Considering the challenges, some people argue MOOCs will soon evaporate (蒸发). But they certainly provide good opportunity for widening higher education, are a means of raising awareness of universities to audiences of tens or hundreds of thousands, and are well worthy of serious consideration.