求问一道三空题

xinxxj

When Eric Temple Bell, in his 1937 work Men of Mathematics, related the anecdote about German mathematician Carl Gauss's
precocious summation of integers as a schoolboy, he was (i)_____one of his (ii)____: Bell had always been praised as a highly (ill)_____ writer, but in this case it undermined his credibility as a biographer.
Blank i
A forgetting about
B drawing from
C betrayed by
Blank ii
D literary strengths
E profound theories
F earlier publications
Blankiii
G imaginative
H meticulous
I productive

答案给的BDG，想求问中间空所在的那句是什么意思呀？
最后一句转折后说这样会损害他的可信度，那转折前第三空为什么不选H呀