The writing system of a language is always a later invention used to record speech,thus there are still many languages in today's have no .... ()

A. μm
B. μg
C. cm
D. inch
E. dm

A. 离心技术
B. 电泳技术
C. 电子显微镜术
D. 光学显微镜术
E. 原位分子杂交技术

A. Leuwenhoek
B. Hook
C. Virchow
D. Schleiden和Schwann
E. Watson和Crick