The true statements about homologous chromosomes are:
A. They are about the same size.
C. Homologous chromosomes contain the same types/sequences of genes.
The other statements are false:
B. They have different sequences of genes and different structures. (This is not true for homologous chromosomes; they have the same types of genes, although the alleles may differ.)
D. One is big and one is small. (Homologous chromosomes are typically similar in size.)