材料：

A block may not only indicate the insertion of new information，but also the omission of matter previously shown．The text of the Notice should invariably be read carefully．The limiting lines of a block are determined for convenience of reproduction．They need not be strictly adhered to when cutting out for pasting on the chart，provided that the preceding paragraph is taken into consideration．Owing to distortion the bocks do not always fit the chart exactly．When pasting a block on a chart，therefore，care should be taken that the more important navigational features fit as closely as possible．This is best done by fitting the block while it is dry and making two or three pencil ticks round the edges for use as fitting marks after the paste is applied to the chart．

问题：

DISTORTION means that ______．

A.the change in form of the block

B.extract of in form of the block

C.the extension in form of the block

D.the increasing of the data in the block

When cutting out and pasting the block care should be used to ensure that ______．A.it be dry enough

B.pencil should be used properly

C.the limits are adhered strictly

D.the more important navigational features fit as closely as possible

The block is not used to ______ ．A.show omissions

B.provide new information

C.make corrections to the Notice

D.change the shape of the charts

The block should be ______ on the chart．A.pasted

B.drawn by pencil

C.fitted

D.put