You may auto-fit rows height having merged cells via Aspose.Cells (although this may not be supported in MS Excel manually). See the updated sample code which works fine for your needs:
Workbook workbook = new Workbook();
//Get the first (default) worksheet.
Worksheet sheet = workbook.Worksheets;
//Get the cells in the sheet.
Cells cells = sheet.Cells;
//Merging two cells (B5:C5)into a single cell(B5).
cells.Merge(4, 0, 1, 5);
Cell cell = sheet.Cells[4, 0];
Style style = sheet.Cells[4, 0].GetStyle();
style.IsTextWrapped = true;
//Put some value into the merged cell.
cells["A5"].PutValue("Please select the conversion rate and velocity between each stage for the waterfall type you selected in the prior question. For reference, we have included definitions of each stage.Marketing through tele – Marketing sources an inquiry that passes through a telequalification function before acceptance/rejection by a field sales force. Inquiry: The total number of raw responses or hand-raisers to an outbound or inbound marketing activity. Relatively little is known about the prospect at this point. Automation qualified lead (AQL): A lead that has been qualified via an automated system or tool and is deemed ready for a receiving function to work. Teleprospecting accepted lead (TAL): A lead that has been formally accepted by the teleprospecting function, which is then compelled to work the lead in a given timeframe to promote or disqualify it. Teleprospecting qualified lead (TQL): A lead that has been qualified via teleprospecting and is deemed ready for a receiving function (e.g. field rep, channel partner) to work. Sales accepted lead (SAL): A lead that has been formally accepted by the sales function, which is then compelled to work the lead in a given timeframe to promote or disqualify it. Sales qualified lead (SQL): A lead that has evolved into opportunities – complete with estimated revenue and timeframe to close. Won business: An opportunity that has converted to a closed/won deal.");
AutoFitterOptions options = new AutoFitterOptions();
options.AutoFitMergedCellsType = AutoFitMergedCellsType.EachLine;
//Save the file.
Hope, this helps a bit.