A. Bill Gates had originally rejected the idea of a dedicated browser, but in 1997 on hearing that the Netscape browser had demonstrated the potential to make Windows obsolete, he
two "had" \,don't know which event took place first. the rejection or the demonstration . incorrect
B. Even though Bill Gates originally rejected the idea of a dedicated browser, in 1997 on hearing that the Netscape browser demonstrated the potential to make Windows obsolete,
"even though bill gates....,......,invested .." makes no sense as a required subject in missing before "invested". who's investing ???
C. Even though Bill Gates originally rejected the idea of a dedicated browser, but in 1997 after hearing that the Netscape browser had demonstrated the potential to make Windows obsolete, he
this whole sentence is past tense. which event happened first is unclear.
D. Bill Gates originally rejected the idea of a dedicated browser, but in 1997 on hearing that the Netscape browser had demonstrated the potential to make Windows obsolete, he
seems fine .hold on
E. Bill Gates originally rejecting the idea of a dedicated browser, but in 1997 on hearing that the Netscape browser had demonstrated the potential to make Windows obsolete,
can't say it's absolutely wrong but it's not as good in conveying the message as option D is. in E, seems like bill gates rejected the idea the same time he invested in it.
IMO D