 <translate> A. 13 (can be weighed by keeping weights of 10, 2 and 4 )
B. 15 (cannot be weighed)
C. 17 (can be weighed by keeping weights of 10 and 7 kg)
D. 19(can be weighed by keeping weights of 10, 2 and 7 kg)
E. 21 (can be weighed by keeping weights of 10, 7 and 4 kg) So the final answer is (B). <yor> A. 13 (a lè wò ó nípa pípèsè àwọn òṣùwọ̀n 10, 2 àti 4) B. 15 (kò lè wúwo) C. 17 (a le wọn wọn nipa fifi awọn iwuwo ti 10 ati 7 kg) D. 19 ((a le wọn wọn nipa fifi awọn iwuwo ti 10, 2 ati 7 kg) E. 21 (a lè wọn wọn nípa pípèsè àwọn òṣùwọ̀n tí ó tó 10, 7 àti 4 kg) Nítorí náà ìdáhùn tí ó kẹ́yìn ni (B). 