Mole =4.4/44=1,==mole =molecule/na then least molecule contains a and c

Explanation:
To determine which compound contains the least number of molecules, we need to use the concept of the mole.

What is a Mole?
A mole is a unit of measurement that is used to express the amount of a substance. One mole of any substance contains Avogadro's number of particles, which is equal to 6.022 x 10^23. Therefore, one mole of CO2, NH3, CH4, and SO2 contains 6.022 x 10^23 molecules of each compound.

Calculating the number of moles in each compound:
To calculate the number of moles in each compound, we use the formula:

moles = mass/molar mass

The molar mass of CO2 is 44 g/mol, NH3 is 17 g/mol, CH4 is 16 g/mol, and SO2 is 64 g/mol.

a. 4.4g CO2
moles of CO2 = 4.4 g / 44 g/mol = 0.1 moles

b. 3.4g NH3
moles of NH3 = 3.4 g / 17 g/mol = 0.2 moles

c. 1.6g CH4
moles of CH4 = 1.6 g / 16 g/mol = 0.1 moles

d. 3.2g SO2
moles of SO2 = 3.2 g / 64 g/mol = 0.05 moles

Calculating the number of molecules in each compound:
To calculate the number of molecules in each compound, we multiply the number of moles by Avogadro's number.

a. 4.4g CO2
Number of molecules of CO2 = 0.1 moles x 6.022 x 10^23 = 6.022 x 10^22 molecules

b. 3.4g NH3
Number of molecules of NH3 = 0.2 moles x 6.022 x 10^23 = 1.2044 x 10^23 molecules

c. 1.6g CH4
Number of molecules of CH4 = 0.1 moles x 6.022 x 10^23 = 6.022 x 10^22 molecules

d. 3.2g SO2
Number of molecules of SO2 = 0.05 moles x 6.022 x 10^23 = 3.011 x 10^22 molecules

Conclusion:
Out of the given compounds, SO2 contains the least number of molecules with 3.011 x 10^22 molecules. Therefore, the correct answer is option (d) 3.2g SO2.