can't click button or submit form using Selenium

I'm trying to use Selenium w/ Python to click on answers to problems posted at a tutoring site, so I can take tests over the command line.

I enter the following:

from selenium import webdriver
from selenium.webdriver.common.keys import Keys
driver.get('https://www.varsitytutors.com/sat_critical_reading_diagnostic_1-problem-10821')

(an annoying popup comes up at this point -- we can ignore that for now)

Answers on the page are embedded in forms like this:

<div class="question_row">    
            <form class="button_to" method="post" action="/problem_question_answers/save_answer?answer_id=539461&amp;problem_id=5065&amp;qotd=false&amp;question_id=10821">
            <input id="answer_539461" class="test_button" type="submit" value="select" /><input type="hidden" name="authenticity_token" value="LE4B973DghoAF6Ja2qJUPIajNXhPRjy6fCDeELqemIl5vEuvxhHUbkbWeDeLHvBMtEUVIr7okC8Njp4eMIuU3Q==" /></form>
            <div class="answer">
              <p>English dramatists refused to employ slang in their work.</p>
            </div>
            <div style="clear:both"></div>
          </div>

My goal is to click an answer such as this one in order to get to the next question using Selenium.

I thought it might be as easy as doing this:

answer_buttons=driver.find_elements_by_class_name('test_button')
answer_buttons[1].click()

But I get error messages saying that the element is out of the frame of the driver.

I've also tried submitting the form, which doesn't produce an error message:

answer_forms=driver.find_elements_by_class_name('button_to')
answer_forms[1].submit()

But it redirects to a different url that doesn't load: http://www.varsitytutors.com/sat_critical_reading_diagnostic_1-problems-results-d9399f1a-4e00-42a0-8867-91b1c8c9057d

Is there any way to do this programmatically, or is the website's code going to prevent this?

Edit:

With some help I was able to click the button once initially. But an identical submit button (by xpath) for the next question remains unclickable. This is the code I'm presently using:

driver.get('https://www.varsitytutors.com/practice-tests')

# click subject
subject=driver.find_element_by_xpath('/html/body/div[3]/div[9]/div/div[2]/div[1]/div[1]')
WebDriverWait(driver,10).until(EC.element_to_be_clickable((By.XPATH,'/html/body/div[3]/div[9]/div/div[2]/div[1]/div[1]')))
subject.click()
# select specialty
specialty=driver.find_element_by_xpath('/html/body/div[3]/div[9]/div/div[2]/div[2]/div[1]/div[2]/a[4]')
WebDriverWait(driver,10).until(EC.element_to_be_clickable((By.XPATH,'/html/body/div[3]/div[9]/div/div[2]/div[2]/div[1]/div[2]/a[4]')))
specialty.click()
# select test 
taketest=WebDriverWait(driver,10).until(EC.element_to_be_clickable((By.XPATH,'/html/body/div[3]/div[8]/div[3]/div[1]/div[1]/a[1]')))
driver.execute_script("arguments[0].click();", taketest)    

# click away popup
button=WebDriverWait(driver,5).until(EC.element_to_be_clickable((By.XPATH,"//button[contains(.,'No Thanks')]")))
button.location_once_scrolled_into_view
button.click()

# select first choice
choice=WebDriverWait(driver,20).until(EC.element_to_be_clickable((By.XPATH,'/html/body/div[3]/div[7]/div[1]/div[3]/div[1]/form/input[1]')))
driver.execute_script("arguments[0].click();", choice)    

I repeat this code again over the next few lines. It has no effect, however; the drive stays on question two and the next few clicks don't work...

choice=WebDriverWait(driver,20).until(EC.element_to_be_clickable((By.XPATH,'/html/body/div[3]/div[7]/div[1]/div[3]/div[1]/form/input[1]')))
driver.execute_script("arguments[0].click();", choice)
choice=WebDriverWait(driver,20).until(EC.element_to_be_clickable((By.XPATH,'/html/body/div[3]/div[7]/div[1]/div[3]/div[1]/form/input[1]')))

driver.execute_script("arguments[0].click();", choice)