Martyrs (shaheed) are alive

Allah says that say not of those who are killed in the way of Allah, "They are dead.'' Nay, they are living, indicates that the martyrs are alive and receiving their sustenance.
Hadith
The Holy Prophet(PBUH) said :
"The souls of the martyrs are inside green birds and move about in Paradise wherever they wish. Then, they take refuge in lamps that are hanging under the Throne of Allah.
Your Lord looked at them and asked them, `What do you wish for' They said, `What more could we wish for while You have favored us with what You have not favored any other of your creation. He repeated the question again. When they realize that they will be asked until they answer, they said, `We wish that You send us back to the earthly life, so that we fight in Your cause until we are killed in Your cause again because of what they enjoy of the rewards of martyrdom.
Allah then said, `I have written that they will not be returned to it earthly life again.

Sahi Muslim

Hadith
The Holy Prophet(PBUH) said :
The believer's soul is a bird that feeds on the trees of Paradise until Allah sends it back to its body when the person is resurrected.

Imam Ahmad .

Thus, the fact that the Qur'an mentions the martyrs in particular in the above Ayah serves to honor, glorify and favor them (although the other believers share the rewards they enjoy.

Source: Q.Tafseer Ibn -Kathir

In the light of surah Al-baqra : 154