A - Thanks for the Question! It depends on what you mean. But, I am guessing what you are really asking is "can a deacon preside at a Catholic wedding?" If this is the question, then yes he can.
But, matrimony is the only Sacrament where the deacon/priest/bishop who presides is not the minister of the Sacrament. The couple is actually the ones who confer the Sacrament upon one another. This is why for a marriage to be sacramental, both spouses must be baptized Christians. Because a non-Christian cannot confer a sacrament upon a Christian. Likewise, a Christian cannot confer a Sacrament on a non-Christian, except in Baptism.
The Catechism tells us:
1623 According to Latin tradition, the spouses, as ministers of Christ's grace, mutually confer upon each other the sacrament of Matrimony by expressing their consent before the Church. In the tradition of the Eastern churches, the priests (bishops or presbyters) are witnesses to the mutual consent of the spouses, but for the validity of the sacrament their blessing is also necessary.