Francis Presto Blair, Jr ______ born in Kentucky, lived and worked in Missouri. [ ]

A. was

B. he was

C. although

D. which was

为了避免在版面设计中不断重复使用基本形或线条使版面呆板，将他们的形状、大小、方向做一些适当的变化，使版面变得灵活。这种形式原理属于（）.

A、对比与调和

B、重复与交错

C、节奏与韵律

D、变异与秩序