胃十二指肠溃疡急性大出血主要临床表现为
A. 突发上腹剧痛
B. 呕血黑便
C. 肠鸣音消失
D. 腹肌紧张
E. 呕吐宿食
Constituent structure rules are generative.()
'Consonants all involve the vibration of the vocal folds.()
Inflectional morphology is concerned with the study of inflections of words in language.()