天然气是当今世界上最重要的气体化石燃料，其主要成份是______．第28届国际地质大会提供的资料显示，深海底有大量的“可燃冰”（固态天然气水合物），可满足人类1000年的能源需要，但现在的开采技术尚未成熟，原因是“可燃冰”的存在环境是______温______压（填“高”或“低”）．

A client being evaluated in the emergency department complains of chest pain that radiates to his neck, shoulders, back, and arms, which decreases when he sits up and leans forward. Based on this assessment, the nurse suspects that he has（）

A. developed another myocardial infarction (MI).

B. endocarditis.

C. pericarditis.

D. myocarditis.