Many things have changed in astronomy over the past half-century. Until about 30 years ago,there was a great    31    of charts and catalogues. Telescopic equipment was limited and there werefew books on practical astronomy. Today, the range of off-the-shelf telescopes and equipment covers almost everything one could need. Electronic calculators and computers have revolutionizedalmanacs and chart production, and    32    the analysis of observations and the publication of results.
       All these advances must surely make this the golden    33    of amateur astronomy. Well, perhaps,but a great deal has been lost as well. Now one may have to travel 80 km to find a sky comparable tothat found in urban areas 60 years ago. The daytime skies are now    34    by aircraft condensationtrails which can    35    for hours and often spread out to form amorphous clouds, making solarobservations impossible and hampering night-time observation too.
【題組】31.
(A) shorthand
(B) shortstop
(C) shortlist
(D) shortage