I am confused in using cin and cout inside a selection

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C++

struct

   #include<iostream>
#include<stdio.h>
#include<cstring>
#include<string>
using namespace std;
void printBook(struct Books book);
void printBorrower(struct borrower borrow);

struct Books
{
	char title[50];
	char author[50];
	char subject[50];
	int book_id;
};
struct borrower
{
	char name[50];
	char course[50];
	int year;
	int id;
};
int main()
{

 Books b1;
 borrower person;
	char opt;

do
{
	cout<<"Enter opt: ";
	cin>>opt;
	if(opt=='A')
	{
	cout<<"Enter Book title: ";
	cin.getline(b1.title,50);
	cout << "Enter Book author: ";
	cin.getline(b1.author,50);
	cout << "Enter Book subject: ";
	cin.getline(b1.subject,50);
	cout << "Enter Book ID: ";
	cin >> b1.book_id;
	}
	else if(opt=='B')
		{
	cout<<"Enter the borrower's name: ";
	cin.getline(person.name, 50);
	cout<<"Enter the borrower's course: ";
	cin.getline(person.course, 50);
	cout<<"Enter the borrower's year level: ";
	cin>>person.year;
	cout<<"Enter the borrower's ID : ";
	cin>>person.id;
		}
	else
		{
		printBook(b1);
		
	//Print Borrower
		printBorrower(person);
		}
}while(opt!='Y');
system("pause");
}

void printBook(struct Books book)
{
	cout<<"Book title: "<<book.title<<endl;
	cout<<"Book author: "<<book.author<<endl;
	cout<<"Book subject: "<<book.subject<<endl;
	cout<<"Book ID : "<<book.book_id<<endl;
}

void printBorrower(struct borrower borrow)
{
	cout<<"Borrower's name: "<<borrow.name<<endl;
	cout<<"Borrower's course: "<<borrow.course<<endl;
	cout<<"Borrower's year: "<<borrow.year<<endl;
	cout<<"Borrower's ID : "<<borrow.id<<endl;
}      

What I have tried:

I tried executing the code but then I cant seem to enter the first statement in every option, If I enter the option A, it will only show the "Enter book title: Enter book author: " and I cant seem to enter anything for the 1st line, same goes to the option B, is something wrong with my code? Is there a limit as to how many cin and cout statements inside a single selection? Please help me. Thank you.