The veil (or curtain) of the Jerusalem temple separated the Holy Place from the Most Holy Place (the Holy of Holies), where God's presence was believed to dwell. Only the High Priest could enter the Holy of Holies, and only once a year on the Day of Atonement (Yom Kippur), to offer blood for the sins of the people. This curtain symbolised the barrier between a holy God and sinful humanity.
According to Matthew 27:51 and Mark 15:38, at the moment Jesus died on the cross, this veil was torn in two from top to bottom. The theological significance, as explained in Hebrews 10:19-22, is that Jesus' sacrificial death removed the barrier between God and humanity. Through His blood, all believers now have direct access to God's presence, not only the High Priest. The tearing from top to bottom indicates that this was an act of God, not of human hands.
The other options do not capture the primary theological meaning. While temple rituals eventually ceased after the destruction of the temple in AD 70, the tearing of the veil specifically symbolised open access to God. The tearing was not an expression of God's grief, nor merely a physical consequence of the earthquake, though Matthew 27:51 does mention an earthquake occurring simultaneously.