What does the word "serendipitous" in Paragraph 8 mean？A．Incidental.B．Suspicious.C．Delight

What does the word precursor in the context in the second paragraph mean？

What does the word "defensive" mean in the passage？ 查

What does the word "altruism" in Paragraph Two mean？A．The quality of being optimisticB．The

What does the word "that" in the last paragraph indicate？A．Branding the rocks.B．Deploying

What does the word“bottlenecks”(Para.2)mean in th

What does the word“defensive”mean in the passage?