20世纪四五十年代以来的第三次科技革命在下列哪些领域取得重大突破

①原子能②电子计算机③微电子技术

④航天技术⑤分子生物学⑥遗传工程[ ]

A．①②③④⑤⑥

B．①②③⑤

C．①②④⑥

D．①④⑤

Tom's grandfather ____ for two years. [ ]

A: died

B: has been dead

C: has been death

D: had died