A. The Bible clearly tells us that Noah had grandchildren after the flood, but says nothing of there being any aboard the ark.
Gen 7:13 In the selfsame day entered Noah, and Shem, and Ham, and Japheth, the sons of Noah, and Noah’s wife, and the three wives of his sons with them, into the ark;
The Bible also clearly says that God preserved Noah and his family.
Gen 7:23 And every living substance was destroyed which was upon the face of the ground, both man, and cattle, and the creeping things, and the fowl of the heaven; and they were destroyed from the earth: and Noah only remained alive, and they that were with him in the ark.
We also read of those who disembarked from the ark:
Gen 8:16 Go forth of the ark, thou, and thy wife, and thy sons, and thy sons’ wives with thee.
Gen 8:17 Bring forth with thee every living thing that is with thee, of all flesh, both of fowl, and of cattle, and of every creeping thing that creepeth upon the earth; that they may breed abundantly in the earth, and be fruitful, and multiply upon the earth.
Gen 8:18 And Noah went forth, and his sons, and his wife, and his sons’ wives with him:
Since the Bible clearly states who went onto the ark and makes no mention of grandchildren, we can only assume that there were none.
We read that Noah sons had children AFTER they disembarked from the ark, just as God commanded:
Gen 9:1 And God blessed Noah and his sons, and said unto them, Be fruitful, and multiply, and replenish the earth.
Gen 10:1 Now these are the generations of the sons of Noah, Shem, Ham, and Japheth: and unto them were sons born after the flood.