1) Alertly 2) Carefully 3) Cautiously 4) In a heedful way 5) In an attentive manner 6) Observantly 7) Paying attention 8) Vigilantly 9) Watchfully 10) With attention 1) Carefully 2) Closely 3) Considerately 4) Diligently 5) Industriously 6) Intently 7) Watchfully 8) Wistly 
[adv] - in an attentive manner
attentively With attention; in an attentive manner.
with attention adverb in an attentive manner; `he listened attentively`