Determining the molecular weight of a polypeptide is an important step in characterizing its structure and function. There are several methods that can be used to determine the molecular weight of a given polypeptide. The correct answer choices are a) Gel filtration chromatography, b) SDS-PAGE, and c) MALDI-TOF mass spectroscopy. Let's discuss each of these methods in detail:

a) Gel Filtration Chromatography:
Gel filtration chromatography, also known as size exclusion chromatography, is a technique that separates molecules based on their size. In this method, a sample containing the polypeptide of interest is loaded onto a column packed with porous beads. The larger molecules, including proteins and polypeptides, are excluded from entering the pores and elute out of the column first, while smaller molecules enter the pores and elute later. By comparing the elution volume of the polypeptide of interest to the elution volumes of protein standards of known molecular weights, the molecular weight of the polypeptide can be estimated.

b) SDS-PAGE:
SDS-PAGE (Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis) is a widely used method for separating proteins and polypeptides based on their molecular weight. In this technique, the polypeptide sample is treated with SDS, a detergent that denatures the proteins and coats them with a negative charge. The negatively charged polypeptides are then subjected to electrophoresis on a polyacrylamide gel. During electrophoresis, the polypeptides migrate through the gel based on their size, with smaller molecules moving faster and larger molecules moving slower. By comparing the migration distance of the polypeptide of interest to the migration distances of protein standards with known molecular weights, the molecular weight of the polypeptide can be determined.

c) MALDI-TOF Mass Spectroscopy:
MALDI-TOF (Matrix-Assisted Laser Desorption/Ionization Time-of-Flight) mass spectrometry is a powerful technique used to determine the molecular weight of proteins and polypeptides. In this method, the sample is mixed with a matrix compound and spotted onto a metal plate. The matrix absorbs the laser energy and transfers it to the sample, causing the polypeptides to ionize and desorb into the gas phase. The ions are then accelerated through a flight tube and detected based on their time of flight to the detector. By measuring the time of flight, the mass-to-charge ratio (m/z) of the ions can be determined, from which the molecular weight of the polypeptide can be calculated.

In summary, gel filtration chromatography, SDS-PAGE, and MALDI-TOF mass spectroscopy are all useful methods for determining the molecular weight of a given polypeptide. Each method has its advantages and limitations, and the choice of method depends on factors such as the size range of the polypeptide, the purity of the sample, and the availability of equipment and expertise.