using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.IO;
public class Test
{
	public static void Main()
	{
		var s = "Since there is limited overhead space on the plane, I assure you, there will be no fee for checking the bags, I can go ahead and fill out all the checked baggage forms for you.";
		var lst = new List<string>() {"no fee, I fill out the forms","some other"};
		var pattern = string.Format(@"(?s)\b(?:{0})\b", 
			string.Join("|", 
				lst.Select(x => 
					"(" + string.Join(@")\b(.*?)\b(",
						Regex.Split(x, @"\W+").Where(t => !string.IsNullOrWhiteSpace(t))
					) + ")"
				)
			)
		);
		//Console.WriteLine(pattern);
		int cnt = 0;
		var res = Regex.Replace(s, pattern,
			g => string.Join("", g.Groups.Cast<Group>().Skip(1)
			.Where(f => !string.IsNullOrEmpty(f.Value))
			.SelectMany((b,i) => i % 2 == 0 ? 
			"<b>" + b.Value + "</b>" : b.Value ) ));
		Console.WriteLine(res);
 
 
	}
}

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