package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	in := bufio.NewReader(os.Stdin)
	out := bufio.NewWriter(os.Stdout)
	defer out.Flush()

	var t int
	if _, err := fmt.Fscan(in, &t); err != nil {
		return
	}

	for tc := 0; tc < t; tc++ {
		var n, m, k int
		fmt.Fscan(in, &n, &m, &k)

		s := make([]string, n)
		for i := 0; i < n; i++ {
			fmt.Fscan(in, &s[i])
		}

		adj := make([][]struct {
			to int
			w  int
		}, n)

		possible := true
		for i := 0; i < n; i++ {
			for j := i + 1; j < n; j++ {
				sameCount := 0
				diffCount := 0
				for p := 0; p < m; p++ {
					if s[i][p] == s[j][p] {
						sameCount++
					}
					if s[i][p] == s[j][m-1-p] {
						diffCount++
					}
				}

				sameOk := sameCount >= k
				diffOk := diffCount >= k

				if !sameOk && !diffOk {
					possible = false
				} else if sameOk && !diffOk {
					adj[i] = append(adj[i], struct{ to, w int }{j, 0})
					adj[j] = append(adj[j], struct{ to, w int }{i, 0})
				} else if !sameOk && diffOk {
					adj[i] = append(adj[i], struct{ to, w int }{j, 1})
					adj[j] = append(adj[j], struct{ to, w int }{i, 1})
				}
			}
		}

		if !possible {
			fmt.Fprintln(out, -1)
			continue
		}

		color := make([]int, n)
		for i := range color {
			color[i] = -1
		}

		ans := []int{}

		for i := 0; i < n; i++ {
			if color[i] == -1 {
				compNodes := []int{}
				queue := []int{i}
				color[i] = 0

				for len(queue) > 0 {
					u := queue[0]
					queue = queue[1:]
					compNodes = append(compNodes, u)

					for _, edge := range adj[u] {
						v := edge.to
						w := edge.w
						if color[v] == -1 {
							color[v] = color[u] ^ w
							queue = append(queue, v)
						} else if color[v] != color[u]^w {
							possible = false
						}
					}
				}

				if !possible {
					break
				}

				count1 := 0
				for _, v := range compNodes {
					if color[v] == 1 {
						count1++
					}
				}

				count0 := len(compNodes) - count1
				if count1 > count0 {
					for _, v := range compNodes {
						color[v] ^= 1
					}
				}

				for _, v := range compNodes {
					if color[v] == 1 {
						ans = append(ans, v+1)
					}
				}
			}
		}

		if !possible {
			fmt.Fprintln(out, -1)
			continue
		}

		fmt.Fprintln(out, len(ans))
		if len(ans) == 0 {
			fmt.Fprintln(out)
		} else {
			for idx, val := range ans {
				if idx > 0 {
					fmt.Fprint(out, " ")
				}
				fmt.Fprint(out, val)
			}
			fmt.Fprintln(out)
		}
	}
}