...
=> The earliest manuscripts and some other ancient witnesses do not have verses Mark 16:9–20 <= Do you believe Mark 16:17-18, "And these signs will accompany those who believe: In my name they will drive out demons; they will speak in new tongues; they will pick up snakes with their hands; and when they drink deadly poison, it will not hurt them at all; they will place their hands on sick people, and they will get well.”
....
Sure I believe all of God's word. To reject any scripture is unwise. Generally speaking, many refuse to accept things they don't believe make sense. But make no mistake, God has a reason for every single jot and tittle in His word. Often times understanding only comes as a result of belief and obedience; it's called faith.
Consider John Mark is the accepted writer of the Gospel of Mark. He went on mission trips with the Apostle Paul. (Acts 12:12, 25; 13:5, 13; 15:37-40) As such, he would have first hand knowledge of the things he penned. I expect your objection to the scripture is the snake and poison reference. See Acts 28:3-6 below. Clearly God has the power to protect His children.
"And when Paul had gathered a bundle of sticks, and laid them on the fire, there came a viper out of the heat, and fastened on his hand.
And when the barbarians saw the venomous beast hang on his hand, they said among themselves, No doubt this man is a murderer, whom, though he hath escaped the sea, yet vengeance suffereth not to live.
And he shook off the beast into the fire, and felt no harm.
Howbeit they looked when he should have swollen, or fallen down dead suddenly: but after they had looked a great while, and saw no harm come to him, they changed their minds, and said that he was a god." Acts 28:3-6
"And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues;
They shall take up serpents; and if they drink any deadly thing, it shall not hurt them; they shall lay hands on the sick, and they shall recover." Mark 16:17-18
"John Mark (Greek: Ἰωάννης Μάρκος, romanized: Iōannēs Markos) is named in the Acts of the Apostles as an assistant accompanying Paul and Barnabas on their missionary journeys.
Traditionally he is regarded as identical with Mark the Evangelist, the traditional writer of the Gospel of Mark." wikipedia