单项选择题
触发器由门电路构成，但它不同于门电路功能，主要特点是（）。
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A.具有翻转功能
B.具有保持功能
C.记忆记忆功能
D.具有置“1”功能
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相关考题
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单项选择题
2. Activities on River Cam Like many rivers, the Cam is extensively used for several forms of recreational activity. These include angling, swimming and various kinds of boating. Angling The water is not murky and is clean enough from its source to its confluence with the Great Ouse to support fish. The fishing rights on the west bank are leased annually to the Cambridge Fish Preservation and Angling Society. The Cam below Bottisham Sluice may still hold burbot, a fish thought to be extinct in English waters since the early 1970s. The last known burbot caught in Britain was in 1969, on the Cam, and in 2010 a fisherman reported spotting two in the Great Ouse. Above Hinxton and Great Chesterford the river holds a stock of wild brown trout, though it is also stocked by the Audley Fly Fishers club and other angling societies who own the rights. Boating All boats require a navigation license from either the Conservators of the River Cam or the Environment Agency. There are public moorings just below Jesus Lock on both sides of the river and on the western bank just north of the bridge at Clayhithe (both with a maximum stay of 48 hours), and unofficial moorings on the railings adjoining Riverside in Cambridge (unlimited stay, but usually fully occupied) which are under review by Cambridge City Council and likely to be reduced to eight or nine formalized residential moorings, or removed altogether. The moorings on the commons in Cambridge (Jesus Green, Midsummer Common map 5 and Stourbridge Common) are reserved by the City Council for holders of its long-term mooring permits. There are also some privately owned moorings. There is a public slipway next to the garden of the Green Dragon pub in Water Street, Chesterton.map 4 This is occasionally used for launching small boats. Swimming The local swimming club's annual swim from the Mill pond to Jesus Green was cancelled for some years in the past because of higher pollution levels. Swimming on the upper river is popular in the summer, and people bathe at Grantchester Meadows all year round. Hardy bathers take part in the New Year's Day swim. 3.What do we know about the River Cam according to the passage？
A．People dislike the recreational activities in River Cam.
B．Burbot was thought to be extinct in English waters since the early 1950s.
C．The last known burbot caught in Britain was in 1969, on the Cam.
D．The River Cam has no pollution. -
问答题
散瞳后视力度数降低是什么原因 -
多项选择题
天然砂是由岩石风化等自然条件作用形成的，如要求拌制的混凝土流动性好，最好选用（）。
A.河砂
B.湖砂
C.海砂
D.山砂
