HomeClass 10 Science Paper AS1 Source of energy 5 Modal with Answer Sheet Paper AS 1 RK Yadav -March 07, 2017 0 What is biogas? How can biogas be obtained? Why is the use of biogas obtained from cow dung advised in preference to burning of cow dung cakes? Tags: Class 10 Science Paper AS1 NCERT Class 10 Science Paper Facebook Twitter