注意力, ちゅういりょく
attentiveness
なるほど持田は最善を尽くしたが、注意力が足りなかった。
が
Particle
1. indicates sentence subject (occasionally object)
2. indicates possessive (esp. in literary expressions)
Conjunction
3. but, however, still, and
after the volitional form of a verb
4. regardless of, whether (or not)