单项选择题The author’s primary concern is to demonstrate that（）.
A．Leif Erikson did not visit AmericaB．Biarni might have visited America before Leif EriksonC．Biarni did not visit WinelandD．Leif Erikson visited Wineland first
单项选择题在语句Z＝X*Y+q＋＋－K中，属于定义性出现的是（）。
A．Z，XB．Z，YC．Z，KD．Z
