#include <cstdio>

#include <cmath>

#include <algorithm>

#include <cstdlib>

#include <cstring>

#include <queue>

#include <iostream>

using namespace std;

#define N 205005

#define lson l,m,tr[rt].ls

#define rson m+1,r,tr[rt].rs

#define ll unsigned long long

#define clear(rt) tr[rt].ls=tr[rt].rs=tr[rt].sum=0;

struct node

{

	int ls,rs;

	ll sum;

}tr[N*20];

struct no

{

	int to,next;

}e[N<<1];

int dep[N],rot[N],fa[N],anc[N],siz[N],son[N],head[N],cnt,a[N],n,maxn,Q;ll val[N];

void add(int x,int y)

{

	e[++cnt].to=y;

	e[cnt].next=head[x];

	head[x]=cnt;

}

void insert(int x,int v,ll c,int l,int r,int &rt)

{

	rt=++cnt;clear(rt);tr[rt].sum=tr[x].sum^c;

	if(l==r)return;int m=(l+r)>>1;

	if(m>=v)tr[rt].rs=tr[x].rs,insert(tr[x].ls,v,c,lson);

	else tr[rt].ls=tr[x].ls,insert(tr[x].rs,v,c,rson);

}

void dfs1(int x,int from)

{

	fa[x]=from,dep[x]=dep[from]+1,siz[x]=1;

	insert(rot[from],a[x],val[a[x]],1,maxn,rot[x]);

	for(int i=head[x];i!=-1;i=e[i].next)

	{

		int to1=e[i].to;

		if(to1!=from)

		{

			dfs1(to1,x);

			siz[x]+=siz[to1];

			if(siz[to1]>siz[son[x]])son[x]=to1;

		}

	}

}

void dfs2(int x,int top)

{

	anc[x]=top;if(son[x])dfs2(son[x],top);

	for(int i=head[x];i!=-1;i=e[i].next)

	{

		int to1=e[i].to;

		if(to1!=fa[x]&&to1!=son[x])dfs2(to1,to1);

	}

}

int get_lca(int x,int y)

{

	while(anc[x]!=anc[y])

	{

		if(dep[anc[x]]<dep[anc[y]])swap(x,y);

		x=fa[anc[x]];

	}

	return dep[x]<dep[y]?x:y;

}

ll s[N];

int main()

{

	int T;

	scanf("%d",&T);

	for(int i=1;i<=200001;i++)val[i]=(ll)rand()*rand()*rand(),s[i]=s[i-1]^val[i];

	while(T--)

	{

		memset(son,0,sizeof(son));memset(head,-1,sizeof(head));cnt=0;maxn=0;

		scanf("%d%d",&n,&Q);

		for(int i=1;i<=n;i++)scanf("%d",&a[i]),maxn=max(maxn,a[i]);

		for(int i=1;i<n;i++)

		{

			int x,y;

			scanf("%d%d",&x,&y);

			add(x,y);add(y,x);

		}

		cnt=0;maxn++;

		dfs1(1,0);dfs2(1,1);

		while(Q--)

		{

			int x,y;scanf("%d%d",&x,&y);

			int lca=get_lca(x,y),f=fa[lca];

			x=rot[x],y=rot[y],lca=rot[lca],f=rot[f];

			int l=1,r=maxn;

			while(l<r)

			{

				int m=(l+r)>>1;

				if((tr[tr[x].ls].sum^tr[tr[y].ls].sum^tr[tr[lca].ls].sum^tr[tr[f].ls].sum)==(s[m]^s[l-1]))

				{

					l=m+1,x=tr[x].rs,y=tr[y].rs,lca=tr[lca].rs,f=tr[f].rs;

				}else

				{

					r=m,x=tr[x].ls,y=tr[y].ls,lca=tr[lca].ls,f=tr[f].ls;

				}

			}

			printf("%d\n",l);

		}

	}

	return 0;

}