Lets see the options one by one.
a) We know R1 ⋂ R2 will give the tuples which are in R1 as well as in R2. As R1 has N1 tuples and R2 has N2 tuples and N1 < N2 , hence minimum possible no. of common tuples = 0 if no tuple is common in them and maximum possible number of tuples is always determined by that relation which has less no of tuples which is R1 in this case.Hence maximum possible no of tuples = N1.Hence A) option is true.
b) Now here in option B , selection operator specifies a condition to select a record hence it is possible that no tuple satisfies the condition and it is also possible that all records satisfy the given condition .In that case all the records will come as a result of selection operation.Since here selection operator is used for R1 , the minimum possible no of tuples will be 0 as explained earlier and maximum will be N1 if all tuples satisfy condition A= 5 and the table R1 contains the attribute 'A'.Hence option B) is also true.
Hence both A) and B) are true.
Hence D) should be the correct option.
Also C) can be invalidated as no attribute is mentioned which is going to be used in projection operation.
