string simuntanous and independent

from sys import stdin

T = int(input())  # Number of test cases

for _ in range(T):
    N, K = map(int, input().split())
    S = list(input())
    
    for _ in range(min(K, N)):
        prev = S.copy()
        new_S = prev.copy()
        changed = False

        for i in range(N):
            if prev[i] == '1':
                new_S[i] = '0'
                if i - 1 >= 0 and prev[i - 1] == '0':
                    new_S[i - 1] = '1'
                    changed = True
                if i + 1 < N and prev[i + 1] == '0':
                    new_S[i + 1] = '1'
                    changed = True

        # If no change happened, break early
        if prev == new_S:
            break

        S = new_S

    print(''.join(S))