So that you may know the certainty of the things you have been taught.
NIV
[My purpose is] that you may know the full truth and understand with certainty and security against error the accounts (histories) and doctrines of the faith of which you have been informed and in which you have been orally instructed.
AMP
That thou mightest know the certainty of those things, wherein thou hast been instructed.
KJV
The angel answered, "The Holy Spirit will come on you, and the power of the Most High will overshadow you. So the holy one to be born will be called the Son of God."
NIV
Then the angel said to her, The Holy Spirit will come upon you, and the power of the Most High will overshadow you [like a shining cloud]; and so the holy (pure, sinless) Thing (Offspring) which shall be born of you will be called the Son of God. [Exod. 40:34; Isa. 7:14.]AMP
And the angel answered and said unto her, The Holy Ghost shall come upon thee, and the power of the Highest shall overshadow thee: therefore also that holy thing which shall be born of thee shall be called the Son of God.
KJV
Many have undertaken to draw up an account of the things that have been fulfilled among us
NIV
SINCE [as is well known] many have undertaken to put in order and draw up a [thorough] narrative of the surely established deeds which have been accomplished and fulfilled in and among us
AMP
Forasmuch as many have taken in hand to set forth in order a declaration of those things which are most surely believed among us,
KJV