from typing import List


def get_row(row: List[str], cells_per_row: int, cell_tag: str):
    """
    :param row: list of cell contents
    :param cells_per_row: how many cells per row
    :param cell_tag: tag name for the cell, td and th being the possibilities known.
    :return: html describing the row
    """
    html_row = "\n<tr>\n"
    for i, cell in enumerate(row):
        if i == cells_per_row:
            # sub-divide natural row width:
            html_row += "\n</tr>\n<tr>"
        html_row += "<{}>".format(cell_tag) + cell + "</{}>".format(cell_tag)
    return html_row + "\n</tr>"