To introduce subtraction of two-digit numbers in Class III, a teacher proceeded in the following steps
Step I Revision of two-digit numbers with understanding of place value system.
Step II Use of tally marks to show that smaller number can be subtracted from larger number.
Step III Application of subtraction on numbers under each column of place value.
In this case, teacher is developing the lesson

Options

A. from system concept `rarr` operation `rarr` algorithm
B. from operation `rarr` system concept `rarr` algorithm
C. from algorithm `rarr` system concept `rarr` operation
D. from system concept `rarr` algorithm `rarr` operation

Answer

D