Many accidents ______ by careless drivers last year. A: are caused B: were caused C: was caused D: caused

9. _______________ is one of the suprasegmental features. A: Voicing B: stop C: Deletion D: Tone

The<br/>effective inversion charge mobility is dependent of the electric<br/>field at the inversion layer and temperature.( )

Why does the existence of intermediate state in the 4-level laser can promote the production of laser beam? A: reach population inversion between ground state and metastable state B: reach population inversion between ground state and intermediate state C: reach population inversion between ground state and pumped state D: reach population inversion between intermediate state and metastable state

Omissions in my recent article ____ confusion. A: can have caused B: can be caused C: must have caused D: must be caused